I'm not convinced that they're paying though the nose. You'll easily spend a lot more in just salary costs trying to attain the same combination of reliability

I'm not convinced that they're paying though the nose. You'll easily spend a lot more in just salary costs trying to attain the same combination of reliability and thoughput on off the shelf hardware. Most shops won't need it, but there's a reason many financial institution are still using these, and it's not because it's all legacy software due for replacement.