I will admit that it is harder to get to t4. However, all tech got scaled back. T4 is more expensive because it is a special tier that gives access to nondoctrinal heavy armor. The pwerfer and arguably brummbar may be underperforming, but if the panther/ brummbar came too early, they would also break balance.
You can always tech up later in the game if you are floating fuel from not losing tanks. Allied factions don't have that choice.
The OKW Panther can hit the field quite early and it isn't OP. And considering the worse stats of the Ostheer Panther I don't really see how T4 getting a major cost reduction would really hurt much with how meh the units in the tier other than the Panther are.
I mean the Panther is a specialist tank, it's countered by AT guns and tank destroyers still have a reasonable chance to pen it's armor. I really don't feel like it hitting the field not super late in the game would impact much.
People keep saying it's a luxury, but it just feels like a chore to me.