According to Burchfield:
oligopsony (from the prefix oligo–, Greek ὀλίγος ‘small’, in plural [ὀλίγοι] ‘few’, and ὀψωνειν ‘to buy provisions’) first recorded in 1943 in the sense ‘in marketing, a situation in which only a small number of buyers exists for a product’ […]. 
Other definitions emphasize that in addition to a small number of buyers, oligopsony often implies a large number of sellers. Now, this struck me as the mot juste, indeed parfait, for describing the situation in publishing scholarly books about J.R.R. Tolkien. A great many people are producing (or want to produce) them, but there aren’t nearly so many buying them. Indeed, I have it from several people in a good position to know that most monographs on Tolkien sell no more than a few hundred copies. That sounds like an oligopsonistic marketplace to me!
As a side note, Robert Burchfield has a direct connection to Tolkien himself — or had, I should say; he passed away in 2004. But long before that, he studied under both Tolkien and Lewis at Oxford. During Burchfield’s last couple of years there, Tolkien supervised his graduate work on “an edition of The Ormulum, a late-12th-century text the language of which requires knowledge of the early Scandinavian languages as well as, of course, Old and Middle English. Tolkien had the necessary erudition, and was an inspiring supervisor” . His accomplishments were too numerous to list here, but a few of the most relevant for students of Tolkien:
- He worked on the Oxford English Dictionary, as Tolkien had done decades before; and in fact, Burchfield eventually became Chief Editor, something Tolkien never did.
- He contributed an essay, “Ormulum: Words copied by Jan van Vliet from parts now lost”, to the Tolkien Festschrift, English and Medieval Studies Presented to J.R.R. Tolkien on the Occasion of his Seventieth Birthday (eds. Norman Davis and C.L. Wrenn, Allen & Unwin, 1962). Burchfield’s essay runs on pp. –111.
- Also in 1962, and in the year leading up to it, Tolkien completed his edition of the Ancrene Wisse with assistance from Burchfield .
- Over the course of roughly the same years again, culminating in 1966, Burchfield assisted C.T. Onions with The Oxford Dictionary of English Etymology. Onions was one of the editors of the OED during Tolkien’s time there almost a half-century earlier, and he was one of the “Four Wise Clerks of Oxenford” Tolkien gently lampooned in Famer Giles of Ham (the other three were Murray, Bradley, and Craigie).
- Finally, a point not relevant to Tolkien, but I can’t resist pointing it out: Burchfield was a Kiwi, just like another of my favorite etymologists of roughly the same years, Eric Partridge.
I highly recommend his book, The English Language. It’s different in many respects from similar books (such as those of David Crystal, Charles Barber, Bill Bryson, and of course, Eric Partridge). The Birmingham Post — paper of record in Tolkien’s old stomping grounds — described it as “so skilfully [sic] written that it must surely take a place among the best three or four books ever written about our language.” I certainly agree, but sadly, Burchfield’s book seems to have gone out of print. Well, scholarly books on the history of the English language are an oligopsonistic market. So it goes.
 Burchfield, Robert. The English Language. Oxford Language Classics. Oxford: Oxford University Press, 1985; revised and reprinted, 2002, p. 44.
 The Independent. “Robert Burchfield. Workaholic Chief Editor of the Oxford English Dictionaries.” 9 July 2004.
 See Christina Scull and Wayne Hammond’s Chronology for the years 1961–2.