So everyone is different, right? Maybe you are prone to break stuff, so buying expensive glass is out. (Sucks to break a nice piece!) Maybe you have different priorities for how you spend your money, etc. That's why this thread was doomed from the title.
I started collecting glass when I switched over to vaping several years ago. I only buy US (or German, ie. Roor) and would never buy Chinese stuff from DHGate. Again, that's just me and I'm weird (or so my wife tells me)- I also only buy 18mm stuff, lol. DHGate is great for those who don't really "collect" and just want some fun, functional glass. I hear the quality is getting better, BTW.
As for worth of a piece... I always figure if it's quality and made in the US then yea, you pay more, but you also support blowers, jobs, etc. I try to buy when there is a sale, or from Boromarket.com. I've gotten some great deals. Below is a Fab Egg with opals that I got for less than $300 on 420. With it is my favorite Roor. I always bashed Roor thinking that you pay for the label- until I bought one from a shop that was going out of business. Now I have several. I'm looking at one now on AquaLab, but it's not on sale. They do have split payments now, which is dangerous for an addict like myself. Here is the photo: