Ost T3:
10 - 20 + 40 + 20 + 45 + 75 = 170
USF T3:
50 - 15 + 120 = 155
Sov T4:
40 - 50 + 80 + 90 = 160
A USF player who rushes their T4 out will be forsaking bars, and healing. A soviet player will not have molos/ AT nade. An Ostheer player can get their tech out 20 fu faster, but will risk no AT gun.
The prices seem fine to me. All the tech prices to reach medium armor are around the same.
So why exactly would the P4 need a price buff? There is no point making a change just for the lols. Changes are only needed if they are needed.
The Sherman has 120.0/100.0/80.0 pen + 160 armor + HE shells
The P4 has 120.0/110.0/100.0 pen + 180 armor + better veterancy
Soviets first tech is free. The reason why the OKW PIV does just fine is that when it hits the field it can shrug off some AT because it has skirts and it's vet is focused on making it better at what it needs to do giving it excellent scaling. The Ost PIV's vet just makes it more durable (till vet 3 that is) meaning it doesn't really have any scaling till vet 3.
T34/85's and Easy Eights hit the field a lot sooner than they used to, meaning the time the Ost PIV is effective is really small because it won't be long before the tougher more advanced mediums hit the field and just outclass it in everyway.
Not to mention the very high Ostheer teching costs mean that when that Ost PIV hits the field it will already be facing multiple ZiS guns as well as SU-76's.