The DAZ models are very nice and very nicely rigged, there’s no doubt about that, and they look really good brought into UE4. You’ll get no argument there.
The licensing fee is not unreasonable (last time I checked, it was $500/$2500 depending on company size), but it’s still a lot of money for many indie shops who are the most likely to not have dedicated modelers.
The models are also fairly high-poly though (V4/M4 are very high, the Genesis/Genesis2 models are a little more reasonable, but still at the high-end of the range used for cinematic models). Throwing one DAZ model in to a small scene on a machine capable of doing UE4 development isn’t the same having a few dozen rigged characters running around a large world, especially if your game is going to target lower-end computers, older-gen consoles, or mobile devices.
Yes, DAZStudio has a decimation tool, and it works decently well for LODs, but when you start decimating down to more typical game-resolution models, they can start to look bad. Re-topoing by hand or using ZRemesher in ZBush can get you a better result, but it’s a fair bit of work.