It's not cheaper when you consider unit costs, the time of arrival for the tanks is the same since the cheapest unit costs 135 fuel in that tier.
Units costs have nothing to do with it.
Add grenades and racks.At least of them will be unlocked before Major, on the other hand OKW does not need to unlock anything.
Add fuel for Ambulance (while OKW receives "free" healing).
And you end up with 25F (nades are almost must-have) +10F for ambulance (another must have) + 60F for Captain + 120F for Major - 15starting F = 200F.
On the other hand, Schwerer with Med HQ is ready for 150.
First PzIV? - 285.
First Sherman - 310 (325F).
No need to say that PzIV, especially with triple armor bulletin is way superior to Sherman.
First E8 - 340F (355F).
First Panther 325F
First Jackson - 325F. (340F).
First JPIV - 285F.
What if we add racks? Well you can see in bracktes (PzIV can come 40F earlier than Sherman and JPIV 55F earlier than Jackson!!)
I don't find the arrival of those units "at the same time", especially when Panther, unit which is superior to E8, comes 15F earlier while it should come later.
What about MP cost?
If we assume that USF need ambu and grenades (which they need), you must pay 840MP to get Major.
How much OKW must pay to get Schwerer? 600MP (this comes with grenades, of course they are free, and healing).
So, please, get your facts straight.