Taking Germany is 40 IPC
Taking Japan is 30 IPC
Which is cheaper in cost to the allies? Japan by far! Smaller armies, more spread out, harder to defend and counter attack.
Also, who benefits most from killing Japan? WRONG! England then Russia! England should be taking E. Indies and Borneo at least, maybe New Guinea and Philippines before Japan sinks their fleet. With an IC in India, it’s reasonable to expect FIC to fall to England as well. That makes up for any losses in Africa, and you’ll have some. (Think SZ 30 unification, btw. Yes, Japan can sink it, and I beg them to go for it, cause it’s gunna cost them their airforce and their navy to do it.)
Next is Russia who will push into Manchuria and Kwangtung for easy income while America puts up ICs in Sinkiang and China to keep them in Russian hands.
That leaves Okinawa for America, basically.
This means Germany’s facing a Russia earning 30 and an England earning at least 30 give or take depending on what Japan does and focuses on. So what if Germany is earning 45-50 IPC, they’re still being out spent by Russia + England and they don’t have to take Berlin, just hold them until Japan is removed from the game, but not necessarily conquered. (Good to do if you can do it, reasonably, but not necessary if the cost and time are too high.)
Also, during this, it is pretty reasonable to expect America to be sending some units to Europe. Probably 2 a round at start (you DO have 2 transports in the Atlantic on USA 1!) expanded to 4 by round 5 give or take. It’s not that expensive, 6 IPC out of 42 income to start with, that’s 36 IPC for fleet to fight 30 IPC from Japan in the beginning. And that’s if Japan doesn’t build any armies at all, which means if they do that, you’re already effective since they cannot hold back the British, Russians and Americans then.