The PIV should perform better though given the cost difference. It's the most costly non-doctrinal medium in the game. It's a 45 fuel difference hence why the T-34 should get a MP reduction to represents its need for numbers and more powerful MGs to make it more of a threat to infantry when the main cannon's on its long reload.
It's not about the cost difference, this can easy be fixed -just increase cost and buff t34-. The key is, for what do we need a cheap tank in t4 that is useless by the time it hits the field?