Teching costs are teching costs, unit costs are unit costs. One is for timing, one is for performance.
People that want to increase prices for things like the MG34 because OKW now got normal ressource income have to consider that nades or tanks (like the Panther) didn't cost less because of the fuel penalty. That also means: higher income does not justify higher prices (only higher teching costs).
#logic
I don't think we would want higher prices for higher income either. People would like to see fair prices since the munition/fuel resources are stabilized for OKW. Obers 60 munition LMG for example is a bit too cheap for it's performance and effect on the squad all together.