Your logic is also flawed the Ostheer Panther is higher tier, higher pop and more expensive TD than the Su-85 thus it should perform better than than SU-85.
But you are missing the point. The point is not how good one trade with the other but how much better SU-85 trade at vet 2 although it vet faster.
If Su-85/Panther relationship is correctly balance at vet 0 the Panther is simply UP at vet 2.
1. They are both the end game TD of the respective faction. And even then your argument works only for OST, since OKW needs to build T4 anyway.
2. For the numbers:
Panther needs 7 shots face-to-face to kill a SU85
SU85 needs 9 shots face to face to kill a Panther
Cost-corrected this pushes the SU85 up to a price of 450 MP / 167,14 FU / 19,29 POP
For comparison Panther: 490 MP / 185 FU / 19 POP
EDIT: this is the average shot number (corrected for accuracy and pen chance, neglecting collision hits) that the tank needs to fire to kill its opponent.
Panther is therefore slightly underperforming is a performance-to-cost perspective. But you get a more sturdy unit against mediums and AT guns. And also a turret.
At least in this case, I don't think the balance is that far off.