I don't know. I've always found munition investment to have a more profound impact on the game for Axis than it has for Allies. Comparing the pair in a very general context:
- Axis = Long term munition investments to further enhance units and has a very predictable influence on each engagement. These munition investments can be partially mitigated by good micromanagement from the Allies player.
- Allies = Short term munition investments including grenades, off-map strikes and few weapon upgrades unless doctrine provides otherwise. These munition investments can be completely mitigated by good micromanagement from the Axis player.
Wehrmacht has as you say the most consistant or as I like to say 'easiest' munition expenses. All you really need to invest into is grenadier LMG upgrades and the rest of your munitions is just icing on the cake for everything else.
OKW base units already come with. The only thing that stands out as a must have upgrade is the panzershreck, but only if your opponent gets armour. Otherwise just keep investing it into well timed grenades. The comparison between the OKW and SOV mine is a bit illogical as well. Squad wiping with a single mine because squad size differences/pathing does not bare context to munition investment. Not to mention what a OKW/OST minefield can do to a single retreating USF/SOV squad.
Soviets have nothing to dump their munitions into asides from mines. Molotovs, AT nades and ability spam are only used when required and they can avoided by the Axis player anyway. Molotov can force predictable influences on the battlefield in the right positions but that is about it. Everything is high risk, high reward munition investments. I just float munitions as Soviets to burn on more reliable things including mines, recon runs, strafes and off-map strikes.
USF currently perhaps has the worst favoured munition investments in the game, not only because of their low performance but the fact they have a great influence on your future unit composition. Having anti-infantry or anti-tank capablilites in your army is a difficult thing to balance and mistake in judgement can be extremely punishing! Especially in the current meta, this option for USF versatility does more harm than good. USF grenades are high risk, high reward as well and are easily mitigated in high rank play. I just upgrade this for the smoke grenade upgrade and the 6-8 pineapple nades that I'll throw because I know my opponent will not have the time to react to simulatenous grenades.
In my eyes Axis upgrades are superior at the moment for their consistancy and reliance. I couldn't care less if I have to pay more for an upgrade that is less dependant on my opponents errors and can be used in almost every situation in the game.
Not to mention your also forgetting the MP/fuel cost associated with a lot of the SOV/USF upgrades when compared to OST/OKW for core infantry. That in itself compensates the OKW/OST player by having more units on the field compared to SOV/USF.