There's a coarse option: Set up a budget and then a budget action. While ECS doesn't have GPU capabilities, the equivalent here would be "IAM action of budget sets deny on expensive service IAM action" (SCP is also available, but that requires an AWS Org, at which point you've probably got a team that already knows this)

It's coarse because it's daily and not hourly. However, you could also self-service do some of this with CloudWatch metrics to map to a cost and then have an alarm action.

https://aws.amazon.com/blogs/mt/manage-cost-overruns-part-1/