It's really horrendous how much the battalion size changes IC cost. Something is definitely horribly wrong when you can have 8kph superheavies being CHEAPER than medium while also having better stats...
It's not even just the battalion sizes, the base costs are way out of whack. Heavier tanks are under-costed.
Historically, as the first example that came to mind, the Tiger I cost thrice what the contemporary Pz IV design (ausf. G) did per chassis. That was a particularly cheap Pz IV, to be fair, but even for the F2 or something it'd be roughly 1 Tiger = 2 Pz IV = 4 Stug III.
Let's call it ~22 IC to make a reasonable approximation of the Pz IV model, ~30 IC to make a reasonable Tiger. That means that the relative pricing of the Tiger is 1.36 Pz IV, so between 68% and 45% of the price increase that it would be going off the given cost ratios historically. This seems to hold true for lighter vehicles than the medium as well - in that "bigger" units get a consistently favourable IC balance as well as their smaller unit sizes working in their favour on the IC front.