From: Elvis served 3rd Armored, Friedberg, West Germany
Production tech --- is only good for USA. The rest, HamburgerMeat is correct, there's higher priorities. So you save 200 MMPs over time. Who cares, when you're getting mopped off the face of the Earth and needed real help. You're playing to win the game, not invest in the stock market.
Mobility --- I always buy this for Japan early on. Why? Because all the units showing up Summer 1941 will get it, that's good value and those units need it for battles in Jungles, DEI, Vietnam, wherever. Russia cannot afford it. Brits, Gerry, USA have it, but also expensive that I rarely bother upgrading to it.