Legally speaking, it's totally wrong. But the fact is that they can't easily prove that you don't own the right to use those assets ; and in no way can they do it before they sue you.
You can have bought the asset under your name, while using a pseudonym for your game. You can have used two different pseudonym. You can have asked someone to bought them for you (it's neither totally legal nor illegal). Or you can have someone doing all the 3D part while claiming that you do everything by yourself. All this are valid reason for them to not find you in the (long) list of people who bought this or that asset.
Of course, they could probably start a long journey, identifying every single assets you used, and cross the list of legal owners to see if someone own them all. If not, they'll know that you are a pirate. But there's so many people using Daz in their publicly released creations, that they just can't do this.
Therefore, while what you're doing is illegal, the risks is really, really low.
This being said, remember that a big part of the guys behind those assets are like you. They are amateurs who are good at something and try to earn some money through this. Therefore, alright you don't have the money at start and have to pirate the assets. But you expect to earn some money, and the least you can do is to use a part of it to correct the issue and buy the assets.
