For example I recently read Song of Wrath: The Peloponnesian War Begins by J.E.Lendon. Its paperback, 576 pages, costs 22$. I previously read another one of his - Soldiers and Ghosts : A History of Battle in Classical Antiquity also paperback costs about 18$, 480 pages. And while looking for something else to read from him I found Empire of Honour : The Art of Government in the Roman World this one costs 3 times more - 63$, while being from the same author, also paperback and a bit shorter - 332 pages. And its no isolated example. A paperback of J.F Lazenbys The First Punic War goes for 46$, while paperback of his Hannibal’s War (which might as well be part 2 of his first punic war book) is 19$
I never noticed such wild swings with regular books, those feel somehow more consistent in pricing. So whats the deal with history books? Is it just free market in play or there's some specific weirdness going on?
What I have been told about this: A press needs to sell a certain number of books to make a profit. For academic press books, that number is not super high: maybe 500 copies or so to recoup the production costs (which is most of the expense, since advertising is minimal and the author gets approximately bupkiss). Most of those sales, in theory, are guaranteed by libraries buying copies, but even those sales have decreased a lot in recent years (my university has not bought a new humanities book in years, and has followed the trend of many universities in liquidating most of their hardback holdings in favor of online offerings and "social space" for students).
So if you're a press, do you think that there are, say, 300-400 buyers out there for your book? If the answer is "no," then you jack the price up, and hope the 100 or so library sales alone put you in the black. Which of course is lousy for both the author (nobody reads their book) and other scholars (if we're not in one of those 100 institutions, we don't get to read it easily, unless there's some other avenue available).
There are some presses that are notorious for this "lack of faith" (Cambridge and Oxford UP are notoriously bad for whatever reason — it's not uncommon for them to price a hardcover academic monograph at $60-80). There are some who have better finances than others (e.g. U. of Chicago Press has a guaranteed income stream through the The Manual of Style, and so that gives them some more flexibility than other presses, so I have been told), but ultimately there is a tricky thing going on with academic books because the expected sales are not very high to begin with, and a real "flop" might only sell a few dozen copies.
(The above only applies to prices set by the publishers; this is separate from the used book weirdo price algorithms that Amazon sellers sometimes use. This does not apply to textbooks which have their own pricing ecosystem. I am not a publisher, but I'm friends with several acquisitions editors.)
Some editors have very high prices, supposedly due to less book impression, and so needed a higher margin per items.
Or at least that is the excuse.
For exemple, Brepols or Brill books could be very very expensive, like 100€ for a 350 pages paperback.
Some books could be cheaper also because some editors have sponsors, which contribute to lessen the burden put on the final buyer.
And some books, which are out of print, are just higher in price, for the sheer rarity of them.