Instructive anecdote. I needed a somewhat expensive book and the UW library didn’t have it. So I decided to buy it. Had the Amazon order queued up and ready to go, $45 with free shipping, then had a pang of guilt about the destruction of the publishing industry and decided it was worth paying a little extra to order it directly from the publisher (Routledge.)
From the publisher it was $41, with free shipping.
I think it really did used to be true that the Amazon price was basically certain to be the best price. Not anymore. Shop around!