There were actually two different JagdPanzer IV.
Allket (A) Version has a vertical section
Vs. the "Standard" version
The Germans just couldn't get their act in unison and say "THIS" is the standard, and everybody build the same damn thing the same damn way...
The Americans had some similarities in the Sherman. Everybody knows it was a mass production success, but their are DOZENS of different subtypes of Engine (Wright Aircraft Radial, diesel, chrysler or ford gas engines), Suspension (VVS, HVVS), armament (75, 76, 105, flame, etc), ammunition storage, hulls (cast or welded), etc...
A tank with a mobility kill (track or engine) can still use the turret to fight on. A TD with a casement has a very limited ability to respond after a MK.
The comparison of the production cost of the STug III with the long 75 gun Vs. Tiger would make you think all you need is STuGs... But a well rounded force needs more than just one tool
EDITED - Found this on Wikipedia under the PANTHER article " The cost of a Panther tank has been given as 117,100 Reichmarks (RM). This compared with 82,500 RM for the StuG III, 96,163 RM for the Panzer III, 103,462 RM for the Panzer IV, and 250,800 RM for the Tiger I. "