Agreed on the Stugs; while are better armored than Pz IVs they also have drawbacks which don't seem to be calculated into the cost. For the Sherman vs Pz IV, I personally don't see a real issue. The 75mm KwK 40 L/48 is valued higher than the Sherman 75mm, which seems reasonable.
I had a quick look at CMFB, january 1945, all Regular, normal motivation, fit, +0 leadership, single vehicles:
There are M4 Sherman available at 199 points available (single vehicle), the M4 & the M4A1. However both come with a hefty rarity charge (1600). The Sherman available with 0 rarity points is the M4A3(75)W, which cost 232 points as a single vehicle purchase. If you go for a 76mm with the least amount of rarity, that goes up to 258 points for a M4A3(76)W at 200 something rarity.
Comparing that to a PzIV J with 0 rarity points: 246 points. The Pz IV H is 248 points, but comes with 744 rarity. The Panther VG mid costs 365 points, 0 rarity. A Marder IIIM costs 126points with 333 rarity. A Hetzer cost 282 points (with 267 rarity), Stug IIIG (latest) costs 303 points with 0 rarity. And finally for comparison sake a JagdPz IV cost around 320-330 points, with rarity between 1000-2500. The JPz IV 70 (V) costs 362 points, with 1086 rarity.
I can't remember exactly the differences between the most basic Sherman and the M4A3(75)W, but IIRC it has better armor, optics, mobility and of course the wet storage.
So, at least for CMFB I don't really see that much of a difference. The most basic Sherman is indeed some 50points cheaper than a PzIV. But the more regular Sherman is only 14 points cheaper than a PzIV J.
For CMBN I had a quick check and noticed the M4 & M4A1 still have some rarity there (~200). So in CMBN you can get a M4A1 (cheaper than M4) for 190 points, at 175 rarity. The M4A3(75)W is still 232 points with 0 rarity for the early and mid variants. The Pz IV H late comes at 248 points, 0 rarity while the cheapest IV is the Pz IV J early, 241 points at 0 rarity. So in CMBN there is a bit more difference between the cheapest Sherman and the rarity is less of an impact.
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All in all this shows for at least these settings and in CMFB, that the points difference between PzIV and Shermans aren't that big. Especially with rarity strict/loose, the Sherman you can expect to see (M4A3(75)W) is the one costing 232 points. While the 76mm Sherman is more expensive than the PzIV, although not by much. With loose/none rarity (and CMBN in generall, although not as much), the chances are indeed bigger that you will encounter more 'cheap' Shermans. But also other toys, like JagdPanthers
One could also argue that the price difference between the Sherman M4A1 and the M4A3 is too big for the actual upgrades it gets and that the basic M4A1 should cost ~20 points whatever more. But that's probably debatable.
The only real issue I see is that the turret-less vehicles don't seem to be cheaper than the turreted vehicles. For example a hellcat costs about 150point, while a Marder has a similar price point. A JagdPz IV 70 (V) isn't cheaper compared to a Panther. Worst off from this list is probably the Stug, I reckon that is because it has quite decent side armor which are also valued poitns. So it is even more expensive than a Hetzer, although not by much.
So as a suggestion for people wanting to see more variety, I'd advise the loose rarity setting. I will surely try to negotiate such settings next time I play a QB.
And if someone has the energy to create another discussion at BFC forum, with proper arguments that turreted vehicles should come at a premium over turretless vehicles: go ahead
. I might do it myself one day, but probably not before Syrian forces in CMSF2 will get RPG ammo in QBs. Right now they get like 1 round per squad, negating their only(?) strong point. I guess we all have our petpeeves. ;-)