Are you saying that many are the same product by different manufacturers?
No, I'm not saying that. Look at that list, though. How many of those are from companies (manufacturers, not retailers) that are still in business?
As you investigated those, what libraries do they use? What support does the manufacturer provide? The retailer?
So you would caution at least on the support side, and perhaps om the quality side?
Buying from the manufacturer is the best way to get support. But, before you buy anything, check out the support that the seller advertises. Are they really offering support, of simply pointing you to someone else for support? Most Chinese sellers are making clones, not new designs, and they will send you to the designer of the board that they ripped off for support.
Perhaps ripped off is a bit strong, seeing as how most designs are released as open source. But, the Chinese sellers are doing nothing but taking your money for what may, or may not, be a good product.
They don't support what they sell.
If you are planning to buy a 100 boards, get one from a reputable designer/manufacturer/supporter. Then, suit yourself where you buy the other 99. Don't get one from e-bay, though, and expect it to be supported.
In my opinion, of course.