I just hate it when people that haven't a clue spout rip-off. There is a whole lot more in an OVP than a couple resistors. I only know this because I know what it does and how. It uses a zener diode to shunt all voltage over say 16v to ground.
I haven't a clue how much a zener diode is but if you don't like MBs price try cramming a PC UPS under your hood recalibrated to 12v systems. Its just a smart fuse, damn it.
Bosch Master, ASE Master, L1
33 years MB technician