Earnest question: when is it cheaper for a business to use mainframes rather than x86 clusters? If they are easier to develop on (no need to solve distributed p

Earnest question: when is it cheaper for a business to use mainframes rather than x86 clusters? If they are easier to develop on (no need to solve distributed problems) even if mainframes have a 1000x upfront cost, they would still likely be cheaper over time due to smaller development budgets? Where am I misunderstanding?