High manpower costs on units is a USF thing rather than an Allies thing. Soviet and British units are usually pretty average in terms of price.
USF's manpower costs are high for two reasons. The first is their teching: the net manpower cost of the Lieutenant tier is -100.
The second is cranking up manpower costs was Relic's preferred solution to balancing USF on release, when Rifles were insanely good and the M20 rush won games by itself. That's why the M20 was a ~350 MP unit for so long. That's why the Tac Support M5 cost 350 MP until two patches back.
Patch by patch these costs come down as USF is normalised.
Which is the long way of telling him what I said a page back about the mp costs being in a different context for each faction due to playstyle, effective ranges, teching etc.
He doesn’t listen though, so he’s gonna come back and say “but why should I pay 280mp and ost gets grens for 240mp? It doesn’t make sense!”