They keep purchasing from vendors that have few or no reviews.

OMG that's like number 1 rule of NOT to buy haha. I usually buy from ShopeeMall for authenticity (make sure it's the actual brand's official store), look at reviews for confirmation, etc.. Doesn't have to be expensive, there are other blowers there that are cheaper but branded (1k pesos+ tho). In gadgets I don't usually trust cheap unknown brands cos I don't wanna risk you know the burning, or exploding gadgets, or deal with a broken product a month after use, etc..