If, on the other hand, I know what book I want, the curation is done and I’m not looking for an event, so cheapest seems a reasonable thing to optimize for.
Until you find out that the cheapest source also waits two weeks to send your book. And sends it by a method that takes another four weeks. And doesn't package it properly so it arrives with the spine broken and water damage. And sends you a used book with pages missing. Or might just accidentally send you the wrong book but doesn't have a customer service contact.
The internet used to be a great place for bargains. Now "cheapest" is almost always the wrong choice.
I've mostly stopped buying books from Amazon. I generally buy them from my local bookstore via their website. Because it turns out I like having a local bookstore, and I think Amazon has quite enough money and power already.