wait what? are you saying there are no 8-GPU motherboards period? Not 8 in ATXish form factor? There are plenty of those if you don't mind enterprise prices(or cryptomining reliability and performance if you're going for that)

It's not the pricing that bothers me, it's the inflexibility of using fully-integrated vendors like Dell/HP over custom, vs standards compliant vendors like Supermicro/ASRock. The difference for me lies in the ability to use chassis, power supplies, etc of my choosing, and not have to pay ongoing license fees for access to the BMC.