It's not like you can't port it over to your own infrastructure if AWS starts getting too costly.

Porting to your infrastructure is not a simple task if you're using AWS services beyond EC2 (DynamoDB, SQS, etc.).

And I don't mean this as a criticism of AWS. We're happy users and have no plans to move off. Just don't underestimate the cost of moving.

It is expensive, but it's also possible.