Generally price should reflect performance but then there is also faction design.
HMG-42 is designed to be more cost efficient than other HMG because Ostheer were designed have more cost efficient team weapon and less cost efficient infatry. They already have taken a major blow to their support weapons with nerfs to mortar and the buffs to USF support weapon and they do not need more.
Unless one want to redesign the faction and make grenadier spam viable.
If maxim needs a buff and according to at least one top player is fine one could start by nerf to it counters like reducing the range of the incendiary grenade or moving to SP and replacing with fragmentation one.
I dont want to touch the mg42, its a good mg as is should be. All other mg,s are except maxim and maybe vickers but i dont use that very often.
Volks imo are the most cost effective main line out there. Defenitly far more then anything soviets have stock. So why is the mg34 better and cheaper then a maxim while volks are so much more cost effective?
I think adjusting grenades and ranges of grenades is not the way to go. All grenades are fine in any situation that doesn't involve the maxim. It would make grenades seriously underwelming in the entire game. Just to make the maxim more usable/naded and wiped frontaly less often.
The solution lies with the maxim imo. If its supposed to remain bad at vet0 (wich comes from a unrealistic maxim spam fear imo) price it as such, 260 mp is to high, soviets already dont float mp anyway. And 20 mp less is nothing game breaking it just signals its a worse mg overall and save you 2 to 3 cons models in a game depending how many maxims you get.
My money is on keeping it at 260mp make sustained fire vet 0 increase cost to 30 muni increase cooldown and have vet 1 lower cooldown and price to current stats. If it turns out its to strong increase the maxims price accordingly.