Let me add to that, the people building these games for the most part use assets from the DAZ assets store. That is, they're not making high quality character models, clothing, furniture, trees and all that jazz from scratch, they just modify pre-built assets, and pose them.
While DAZ itself is free, the cost of assets mounts up fast. It's also why after you play a few of these games, you start to recognize the base models. Building high fidelity models, texturing, sculpting, rigging and all the other shit that goes along with it is hugely time consuming and requires much skill, however, so it's not really practical. I think one of the reasons this game is astronomically glacial is that stoper enjoys doing that stuff himself to a degree (I don't follow this game closely for said reason but I remember seeing him write about building an entire set piece/environment himself).