DynamoDB is the same, it charges you for the number of reads/writes you do, so if you're doing full table scans on massive databases, you're going to have a bad time.
There is a difference though - you don’t have a query language that makes it easy to do, and the actual technology pushes you to make a different more correct choice.
I'm all for the aws hate when it's deserved, but if you get screwed by it on billing, you didn't read.