(This is a bit of a ramble; there's no grand argument here, more like some free association,)
In 1980, I was introduced to Piers Plowman in the form of the Clarendon Mediaeval and Tudor Series edition of the first part (i.e. that part corresponding to the A-Text) of the B-text. It was essentially a light reworking by J.A.W. Bennett of Skeat's edition of the late 19th Century, with notes added for students. This was in the context of a course focussed mainly on Chaucer, but I was interested enough in Langland to have written a paper on Piers, but I cannot recall what it said, except that it referenced the passage on the harrowing of hell.
A year later, I was introduced to some of[1] the fighting over modern textual criticism when I took a course in codicology in graduate school under Lee Patterson, in the form of the arguments over the Kane/Donaldson edition of the B-text. (Patterson wrote an article on the issues around the edition, "The Logic of Textual Criticism and the Way of Genius: The Kane-Donaldson Piers Plowman in Historical Perspective", reprinted in Patterson's Negotiating the Past, at about that time.) The editors (put very briefly) identified such a large degree of convergent variation in the editions of the A-Text and B-Text that classic stemmatics became impossible; editing had to be locus by locus. (There has not been universal agreement: Charlotte Brewer in particular was vocal in dismissing the approach. Given that her own analysis has led to the identification of an earlier Z-text which is even more dubious, I'm inclined to agree with Kane.)
[1]The other big argument at that time was over the Gabler Ulysses. That has never really settled down - there's a standard paperback aimed at the academic market using the Gabler text but there are also emphatic holdouts. The Folio edition of Ulysses uses the older text.
About a year after that I purchased a complete Piers Plowman; the EETS edition of the Skeat B-text (second-hand, at Thornton's, in Oxford). This was my reading copy for a good number of years. The Bennett edition was better as far as it went, but dropped about two-thirds of the poem.
The critical edition by the Athlone Press - that is, the George Kane versions, completed in 1999 by a C-text version by Kane and Russell - seemed to have remarkably little effect on what was broadly read. The copies of PP I ran across from time to time in second-hand stores were all based on Skeat - either the EETS version, or the short version by Bennett - and that seemed to reflect what students were reading. The Knott/Fowler edition of the A-Text showed up once (to be grabbed immediately) but the A-Text is really a version for somebody who has already become interested in the poem and wants to see the other versions.
(For some reason, the C-text shows up rarely to not at all second-hand. The student versions were of the B-text until Pearsall's student edition of the C-text in 1978 - but I've never seen the Pearsall in the wild, so to speak, although it has been reissued twice, mist recently in 2008, so it's clearly in use.)
A couple of years ago I found the parallel-text edition by Skeat at the Trinity College Book Sale - a career academic had retired and I was able to also acquire the EETS Gower and a few other Middle English texts as well. This gave me a second copy of the Skeat B-text plus a parallel A-Text and C-text, completing a collection of all three texts after a little over 40 years.
Then, about three months ago, I ran across the Kane edition of the A-Text in a local second-hand bookshop at a decent price. Like all of the Athlone Press versions, it has a long introduction (all about textual editorial principles and the evidence of the MSS) and full textual apparatus. It also happens to be a good reading text[2] with clear type, good page design, and overall very pleasing aesthetics. A check on AbeBooks also indicated that I could get a copy of the Kane/Donaldson B-Text reasonably cheaply, so I ordered it; it arrived late last year on the first day the Post office was back in operation again. It has an even longer preface (which I had read over forty years before) and is an equally good reading copy.[3]. The only problem with the Athlone versions is that they're not necessarily what you want to take on transit; they're hefty hardcovers with about half their pages being given over to the prefaces.
[2]If you know Middle English. There's an extensive apparatus, but it's all textual variants. The Bennett and Pearsall editions would be what to use if you need more glosses and/or context.
[3]Some scholarly editions are run-of-the-mill books. Some show the signs of excellent design, and manage to fill both the demands of scholarly documentation and the reader's experience quite well. Another good example is the standard edition of Tristram Shandy, which is a lovely reading copy. (You can get the text of that edition as that in the newer Penguin Classics edition but, again, with a different kind of apparatus.)
All this raises the general question: in a case where there is a choice of editions of a text, which one should one choose, and why? (It's worse with Shakespeare. Just about every major edition of Hamlet differs from all the others; the degree of variance is less than with PP, but the number of choices is much greater.)
In some cases the key factor is simply expense and availability. To take a simple example of a popular novel: the definitive edition of Jane Austen remains that of R.W. Chapman, and the original books are lovely artifacts. It's one of the last scholarly books I know of printed using catchwords. (And you can get cloth bound volumes second hand for about 40 dollars sometimes.) It remains in print; a current new copy in paperback of one volume is about a hundred dollars. The original was also published in Morocco leather: the full set of five volumes runs about 5,500 (USD) second-hand. But the text itself, minus the apparatus and secondary material, is in the Oxford Illustrated Jane Austen, which is much cheaper (especially second hand). The Folio editions are about 80 USD per volume. If you just want to read the text, regardless of format, Project Gutenberg has free texts based on Victorian editions, and a Penguin Classics text is a cheap but reliable version (largely based on Chapman) and is available second-hand for about five dollars.
All of which resolves itself to essentially five choices:
1) Just want a reading copy, don't care about text, willing to read online: Gutenberg
2) Want a cheap copy to read in hardcopy: Penguin Classics or equivalent (10-20, depending on second hand or new).
3) Want a reliable copy with full editorial detail: from 40-90 dollars per volume, depending on Second Hand (HC) or new (Trade PB).
4) Want a very good hardcover reading copy: from 40 to about 100 (Second Hand Chapman/OUP to Folio).
5) Want the best version available on all counts: 1,100 per volume (Antiquarian leather-bound Chapman edition)
Most readers will fall into categories (1) and (2). (3) is pricey because there's a severe dropoff in demand numbers which affects the economics of publishing really scholarly editions in bulk. (4) is essentially a luxury market. In this case it happens to overlap with the scholarly market, but this market exists for non-scholarly books also. (5) is an extreme form of the luxury market: if you had money to throw away you could treat these as nice reading copies but they fall more into the "collector" space. (They're what Folio pretends to be.)
There are few variants in the text itself, though: the only authoritative source is the first edition, with a couple of corrections which may or may not be made following Chapman.
At the other extreme, consider Joyce's Ulysses. You can get reasonably cheap paperbacks of both the older text and the Gabler text, and there's an unresolved war over the superiority of one over the other. (Older texts, I should say, because there's more than one.) I have a second-hand copy of the paperback of the Gabler text aimed at students and the general reader which cost about 20 dollars or less. The old Bodley Head edition is a very nice reading copy, at 20 to 30 dollars second-hand. At a slightly higher end I was able to pick up the 1999 Folio edition (which is very emphatic about not being the Gabler text) for about 50 dollars. But all of those are simply the text itself. For the apparatus, the three volume Gabler edition with full printing of variants is 750 for three volumes, second hand. That's not that unusual with large works for which the primary market is libraries: the Frankel Agamemnon is 500 dollars, second hand (also three volumes). (By comparison, you can get the very respectable Denniston and Page edition for about 30 dollars.)
In the end, this little associative tour may be more about markets than editions.
The collector's market, the one with $5,500 Jane Austen sets or the edition of the Allen Oxford Classical Texts Homer in calf leather and onionskin[4] isn't really a market in an economist's sense of the word. There's no mechanism for setting an agreed-on value.
[4]This was a real thing. I saw it once in a library copy, and it's a lovely piece of work, and belongs to a vanished world.
The market for the Folio Society isn't really a collector's market, although I'm sure some people collect Folio editions the way some people collect Foulis Press editions, at a lower cost. It's a market for general readers with lots of money who see themselves as book fanciers. (They have shifted away from publishing editions of the classics to publishing the entire Dune series, Marvel comic collections, and Le Carré. I don't think their choices are poor from a marketing perspective, but it declares their market in a way that editions of Trollope, Austen, and Gibbon don't.)
The academic market, like the professional market which I knew on the other side when I was a legal editor, is one characterized by high costs - accuracy and reasonable usability are important - and small audiences, usually libraries and a few dedicated professionals. From a publisher's point of view, unless you are publishing a book which might be put on undergraduate courses, your market is little larger than that which might have been before an eighteenth-century publisher: a set of libraries, plus a smaller number of individuals with the means and interest to purchase your product.
By comparison, the general market is vast. If only one in a thousand people are interested in buying a paperback copy of Clarissa[5], well, that makes forry thousand some potential customers in Canada, two hundred thousand in the United States, and maybe seventy thousand in the UK and Europe. Thus, modernizations of Piers Plowman are vastly cheaper than editions of the original text. This also has a bearing on why, although in general the theory of academic editions relies on copy-text for accidentals, editions of Shakespeare tend to have modernized language: it increases their market many-fold.
[5]I'm not. I read and enjoyed Pamela, but my life is likely to run out before I finish all the books which are in a notional queue before Clarissa.
Commercial authors in the serious midlist area can hope to do rather better[6]. Commercial bestsellers get to maybe one percent of the American public at best but the economies of scale are such that deep discounting still provides massive profits to the publisher and the author.
[6]Better than Piers Plowman modernizations. Doing better than Pride and Prejudice is a different category of challenge.