I was a member of AWS customer advisory board for years. Two dozen of largest enterprises and unicorns and so on. Nobody wanted the billing department "inline" of systems controls.
AWS provides all the controls you need to flip the switch yourself, and provides the CDK / TF / etc. patterns for it. Plenty GitHub projects to host your own light switch service.
Don't relinquish the switch.
And of course, two dozen enterprises trump hundreds if not thousands of other small businesses right? Did AWS think of, oh I don't know, a 'feature flag' or somesuch thing that enterprises and unicorns are so fond of to provide this feature to those who don't have VC money to flush?
But it still does and can only claim having those after building them.
Their customers have been asking for that hard cap feature for a long long time, not building that feature while saying customers have all the tools to build it themselves is just a deliberate misdirection at this point.