One question I've been asking myself lately: are single to maybe double digit price optimizations on books such a dominant concern that I should prioritize them over other values?
For an activity I have to do daily, maybe. That order of savings on meals adds up fast enough to be a triple digit number in a month.
Book purchases are weekly to monthly events, any savings on the order that amazon can give me tends toward a rounding error in a monthly budget. Or if my budget shrinks to the point they're not and I need to conserve funds that badly, I will use a library system.
Speed is nice but it's rarely crucial (and these days publishers themselves can get it in your hands pretty quickly).
Lots of us software engineers know "premature optimization is the root of all evil" -- when you overoptimize early, you commit resources in particular attention towards optimizations you may not know serve your ultimate goals.
Maybe your goals begin and end with getting the book in your hand at the lowest price in the shortest time period.
Maybe your goals include what kinds of businesses, activity, people and therefore society you support economically.