Taobao is the world's largest e-commerce site and the seventh most visited website according to Wikipedia. : P
This not-so-mobile version of the page might be slightly easier to navigate...
https://item.taobao.com/item.htm?id=587279263399
That being said, I haven't bought from them, and I suspect that the vast majority of their customers are in China. And just being a big site doesn't guarantee that the product is legitimate. Even other big online stores outside China like Amazon and Ebay have listings for plenty of "fake" off-brand products from China that don't live up to their description, and that's likely significantly more common over there.
It might potentially be a real RX 570, but it appears to be an off-brand card at the very least, and I doubt it would have any sort of usable warranty, and probably no way of easily returning the card if it turned out not be in proper working order. Without a warranty, and perhaps questionable build quality, you might as well be comparing it to cards on the used market.
What country are you in, and what sort of prices are you seeing for RX 570s where you are?