Sure, where there's demand, there will also be a supply. But prices paid for black market products tend to be high to compensate for the risk that those who sell them take, while product quality tends to be questionable.
Well if you want cheap you should stop vaping, that will solve your problem. Other than that China isn't stupid there will be a low end and a high end market. If you think you'll be paying 50 bucks for a 20 dollar rda believe me it won't happen, China regularly uncuts itself.