How are you distinguishing between a copy and a knockoff? If the same exact pipe has a logo or not?I get your concerns, but without DHGate and similar sources I would have very little glass. I don't support and would not buy labeled knockoff glass that is pretending to be from the original creator, but I have no problem with copies. Nobody is going to mistake my Steven or Yingmin5 or Sunshine Store glass for the original vendors. For the most part they aren't even close. They may (I hope) function well, but their fit and finish is not on the same level.
DHgate glass was affordable a few years ago but it seems like it has gone way up, I'm pretty sure Biao.T charges more than some of my heady American made glass.