I agree. IF the distance between moscow and Germany is too huge, even if Infantry is cheaper, you will have a hard time moving them quickly to the front. My guess is : First few rounds buy INF + Fighters/bombers/tac. Then if you manage to break into the russian lines, buy all tank/mech inf to reinforce your infantry :)
On a defensive position, INF > Tank, always. Even in AA50. But, INF < INF + Tank. Balanced army will always win.
lets see the game before going into the price detail
Rolls: 9@1 8@2 10@3; Total Hits: 89@1: (6, 2, 3, 3, 6, 2, 1, 4, 1)8@2: (1, 3, 6, 1, 6, 6, 3, 4)10@3: (3, 6, 4, 3, 3, 6, 1, 5, 5, 6)