AWS is cheap to start with, but once you got some scale, the numbers starts racking up quickly. It's a really bad idea to use AWS for a project with lots of users and low earnings per user. Of course, for some kind of eCommerce project with millions in turnover the server costs doesn't matter, but for a small company or individual project hosting choice can be the difference between making a decent living or burning money.

Absolutely, and "can I see the billing" is one of the first questions I ask in my head whenever some new platform technology is announced.