Legislatures in states like PA & NC passed laws prohibiting manufacturer imposed reimbursements for warranty work. Only way I could think of stating that.
There is a process in place where you have to provide documentation that you are consistently maintaining an average margin/markup on Customer Pay Repair Orders that can in turn justify the manufacturer should also be subject to.
Documentation would be something to the equivalent of 100 successive CP ROs showing consistent margins being obtained.
A consultant amassed the needed docs on several occasions with intervals in between to provide to GM.
It takes a while to complete, but it's worth the effort.
Makes one helluva difference on high dollar items like complete wheels sets and drivetrain work.
If everyone were doing it, it might make more sense for GM to reconsider some of their ridiculous pricing.