imo at least with dynamodb, its pretty straightforward what any given call is capable of doing, and you can get back capacity usage on every request to track. with these mysql/postgres compatible apis the actual query is abstracted as is its cost.

Yeah the pricing model for SQL based queries is not optimal at all considering you don't control how the query optimizer will use the indexes, and (not trying to assign malice) they aren't very incentivized to improve it.