PEO vs HRIS at 80 EE — when does the math tip toward bringing it in-house?

We are on a PEO right now (~80 EEs, fast growing). Health benefits are good, payroll is reliable, but I am paying a meaningful per-employee admin fee on top of the underlying carrier costs.

As we approach 150 EE, the per-EE fee becomes a real number. Curious where folks have drawn the line between stay on PEO + accept the overhead vs. migrate to an HRIS + take HR back in-house.

What headcount tipped the math for you? What did you under-budget for when you brought it in-house?