Yes, they were very cost-inefficient. And by that I mean, they were labor intensive vs. the number produced.

The Americans and the Soviets produced tens of thousands of M4s and T-34s, in addition to IS-2s, 3s, KVs, M5s, etc. These platforms were simple, and by 1943 were pretty outclassed by the German tanks being built, like the Pz V, and VI. Even the Pz IV was pretty on par with the M4 and T-34 tanks in a way that wasnt true in 1941 (ie, the T-34 was generally considered a better tank than the 1941 variants of the Pz IV). But these workhorse models were built en masse, and they could simply swamp the limited German production, which simply never reached the same levels of either the Soviet or American tank production.

Now, the Pz V, VI, and VII (Panther, Tiger, K. Tiger) were really phenomenal tanks. The Pz V is widely regarded as the paradigm from which modern Main Battle Tanks are designed (in its firepower v. mobility v. defense balance). The problem was, it took more time to build a Pz V than a Pz IV. And the Pz V was kinda junk when it was first mass produced, it had a lot of problems which needed sorting out. By 1944, when those problems had been worked out, the Pz V was probably the best tank of the war, pound for pound, (IMO), but by then there were too many T-34s and M4s for the Pz V to make a difference. For the VI and VII the problem was worse, more resources, more engineering, more teething problems, and more man-hours to produce one vehicle.

The general consensus was, had the Germans focused on building and upgrading the Pz IV, and keeping it competitive vs. the T-34 and M4, the Germans may have done better. The IV was a proven design, it was a good design, and it was smaller and easier to make then the larger V, and especially the heavy tank VI and VII. I would only introduce one wrinkle into that thinking. The problem for Germany was: it could never produce as many tanks as either the Soviets or the Americans, and certainly not both, and certainly not after Lend-Lease flooded the Soviet economy. The Germans needed tanks which could account for multiple enemy kills while remaining effective. The Pz V and VI, on paper, fit this role well. They were powerful, the VI equipped the much vaunted 88mm gun, and they were fairly mobile (especially when compared to the VII and VIII). So those designs did make some sense, especially when you consider that Pz IV production would likely have never reached M4 or T-34 levels anyway.

Just for comparison, think about the Production numbers:

Pz IV: 8500

Pz V: 6000

Pz VI: 1300

Pz VII: 500

Total: 16300

M4: 50000

T-34: 85000

You can maybe see a fundamental problem in scale between the three countries. Germany's production was simply not on the same level as the American and Russian automotive industries.

I'm not sure how the Soviets approached their tank design, but the Americans seem to have used largely off-the-shelf parts to create armored vehicles (which sound like something the Soviets would naturally do themselves). They used their extensive automobile assembly lines, found a use for aircraft engines made obsolescent by improving refining technology, and used a clutch assembly that any grease monkey from a gas station would know how to fix. It made their tanks easy to produce, and easy to maintain in the field. One can easily imagine that the armament on the Sherman might have been better had they realized they needed more firepower when the mass production plans were finalized, but, as it was, they had a vehicle that could outnumber the competition and that was enough.