My money is on them getting neither lower AWS costs nor lower dev costs. They're just paying out both ends because "cloud" is a thought-terminating cliché at this point.
Ditto the bit where "As a last resort, we write our own code". That feels like a lot of pain and YAML trying to cobble together other people's expensive code.
It's all the yummy egress and all the other markups you're paying for.