I just tried Walmart.com (with uBlock Origin). It's 2.4MB, with 32 scripts loaded.
Amazon.com (logged in) was 12MB, with 28 scripts.
Amazon.com (logged in) was 12MB, with 28 scripts.
(Disclaimer: Anecdata for my system, obviously.)
There are substitutes for AWS, but the switching cost is relatively high. Whereas for toothpaste, breakfast cereal, toasters, books etc etc the substitution is perfect (I can buy the same brands from many companies) and switching cost is low (I pull out a credit card).
Insofar as Amazon has a large free cashflow coming off AWS after capital improvements, it can use that money to (a) attract cheap funding from Wall St to (b) build, build, build.
I will say, Amazon's above the fold paint was faster, but it did load a LOT after that.