I use Seymour Duncan's in my '$300 to $800' guitars. The sounds have more depth & definition, definitely worth the extra cost. I used to have Duncan Designed PU's, but they can't compare.
I suspect that like most Asian-made PU's, none of the materials are of the quality of American or European-made PU's. Of crucial importance is the tension and pattern of the windings, and this is super-secret stuff that PU winders keep to themselves. I asked Zhang about this, and said Asian PU's have a tight uniform wind, that looks nice but doesn't do much for tone quality. Just winding a PU to the same ohms reading as another doesn't mean anything. You need to use the same tension and pattern, and I doubt Duncan has given that info to any foreign country; it's too easy for another Asian company to hire Duncan-trained PU winders and mass produce PU's and undercut Duncan's sales. These are closely guarded trade secrets, like the formula for Coke and the Colonel's blend of 11 herbs and spices. This info isn't going to circulate.
Duncan Designed PU's produce sound, but you won't get the quality of tone of a Seymour Duncan PU. If cost is an issue, buy used SD's.