It could be a scammer trying to make the book look rare (https://www.nytimes.com/2018/07/15/technology/amazon-used-pa...), or it could be price-setting bots derailing each other (http://www.michaeleisen.org/blog/?p=358)
”And different ones, too”
How do you know they are? 2 of the 3 ship from Florida; the third doesn’t mention where it ships from. Could be chance, could be a sign that some of them are the same seller.
(And no, I have no idea how common it is for a merchant to have multiple stores on Amazon. It is fairly common on other stores on the internet, though, as it doesn’t cost much to create another web store, and it allows you to target different market segments)
It's the same batch of sellers, selling across most all of those sites. Or to the extent that there are sellers who are, say, on Ebay but not Amazon, or vice versa, they have bots tracking the prices across all the sites. In either case, I find that you just don't get much price variance across book selling sites these days. I mean, sure, there are occasional exceptions, but by and large, prices tend to converge to a common value, or at least to a small range around that.
It's not just 1 seller that has high prices, there are different sellers, selling it for $600-$700 and on abebooks I've seen a $1000.
Am I missing something here?
When I see weird situations like this, I usually assume it's a consequence of algorithmic pricing driven by bots, and that there's a bug, or the bots got caught up in some weird feedback loop or something, and the prices got set to some goofy value.
It could also be that demand for the book did temporarily spike for some reason (maybe somebody famous mentioned it in a popular Youtube video or something) and the pricing algorithms were reacting, but just overshot the mark.
I think something like that happened with Human Universals (https://www.amazon.com/Human-Universals-Donald-Brown/dp/0070...) a while back... it's not really all that notable a book in general, and there are plenty of used copies available. But Alan Kay recommended it in his Startup School videos and when I went to look for a copy, the prices were all totally outrageous. Like, on the order of several hundred dollars for even the paperback edition. But it eventually settled back down... but even now, the cheapest used paperback copy is around $65.00. Maybe it was a coincidence, but I suspect it was related.
But if you want his "Modula-2: A Complete Guide", its only $300 new!
