I can see an argument of "well it typically bogs down and stops being performant at X, and we don't want to get a bad rep because people abuse it, so we don't allow anything over X", but that should still be negotiable if you can show you have plenty of horsepower.
Look I love giving people the benefit of the doubt, but that's not why this pricing model exits. It's because they want to capture a percentage of the value delivered, and the easiest way to do that it to charge by executions
