I would say their base MP Price isn't really the problem it's the cost of Bars that is more of an issue. Having to spend 120 muni on every squad is really expensive and USF is constantly bled for Munitions which I find is also a problem with Ostheer. I would rework Bar's to be similar to what they did with Bren guns. I would nerf the performance of the weapon a bit but make it cheaper so it's easier to double equip your squads to allow you to deal with upgraded Volks and Grens. But it would nerf their peak performance when they get Vet 3 and have 2x Bars. Which I think makes them a bit too powerful but it takes a while to achieve. Rifles are more expensive than Volks and Grens but generally win 1 on 1 engagements to compensate. This issue is they aren't as cost effect long-term. They struggle a bit in the mid game which is kind of where USF is at their weakest imo.
Why not do a global upgrade like in COH1?
Pay 300 manpower, 30 fuel and all present and future Riflemen come equipped w 2x BARs
for free. In COH1, all Sherman 75 present and future changed to Sherman 76 this way, too.
Plus, they had the + bonus (Sandbag armor on the tank) when buying the overpriced top .50 cal pintle.
If you think that's too much, throw in grenade upgrade there too