liars and amazons
Amazon UK lie about their prices.
I'm sure they aren't exactly doing it deliberately, but it's an easy problem to spot, I've pointed it out to them already, and I can't imagine how it could be very difficult to fix.
Here's what happens, as best I can understand it. Whenever they have a book that's available "Used and New" (i.e., from one of their "Marketplace" sellers), they pick a preferred seller in some mysterious way. Then, in your wishlist, instead of presenting you with either the price you'd pay to buy the book from Amazon UK or the lowest price you could get from a Marketplace seller, they present the price being asked by their preferred seller. Except that sometimes instead of doing that they present a much lower price that isn't available from anyone. (Perhaps it's the most recent new price, when the book is only available used.)
You can see several instances in an inelegantly annotated montage of screenshots (642x670, 121k). The left-hand side is the start of my (enormous) Amazon UK wishlist; I didn't choose it to show the problem particularly badly. The right-hand side shows the relevant bits of the product pages for books whose prices are false. Notice that this amounts to fully half the products shown, and that in one case the real price is nearly twice the price shown on the wishlist.
This is stupid and misleading and quite without excuse. And -- gosh, what a coincidence -- it almost always has the effect of making books appear cheaper than they really are. (Because if you buy from a Marketplace seller, you pay more in postage and packaging.) It would be better for the prices not to be shown in the wishlist at all. Better still for them to fix their stupid broken lying system, of course.
(Note to the generous: my Amazon wishlist is not really a wishlist, although there's nothing there I wouldn't be glad to have for free. In the unlikely event that someone reading this is moved to buy me books, asking me for suggestions is likely to be more reliable than picking from my wishlist.)