I think the question of whether to accept a defect on a $30 bubbler from China comes down to how much you value your time. Most of the people who have reported complaints or issues in the past to DHGate or AliEx vendors have been asked to ship the item in question back to China. Personally, it's not worth $30 to me to mess with all that (filling out customs forms alone makes me want to cry), especially since I'm not positive I'd be reimbursed the cost of shipping. If the issues are merely cosmetic (such as the hairline crack my own D020-D has), it's very easy to live with, IMO.
My general sentiment is that if I care about quality, I'm going to pay for it. If I care more about getting a good deal, I have to accept that I'm almost certainly sacrificing quality. The reason I've refused to pay more than about $32 for any piece of China glass so far is because I know that if I get a piece and it sucks, I'm probably not going to want to deal with trying to make it right. $30 is my threshold for "sucks, but won't break my heart (or wallet)".
But that's just me. YMMV.