Yes, thats one way to implement it. It still moves that global billing system into a ring 0 importance with 99.9999% availability and performance requirement, where before it wasn’t even in the picture. Not impossible, just suddenly every single AWS (or GCP or Azure etc) has a global single point of failure that gates all their performance and runtime actions.

Not to mention having no way to network isolate such service as every single service in every single network boundary needs to be able to contact such service, and every service needs (more or less) same auth permissions on all user accounts it’s running.

Again, solvable problems with enough code, but not simple problems by any means if you operate at a large scale.