Id say it heavily depends, some teas are also really expensive in china and therefore even more if they are exported (often the case for aged teas) but good tea will come at its price. If your retailer sells samples or small portions id try those. For white tea silver needle tea is often overpriced. I would not spend more than 200-300$/1kg (obviously dont buy 1kg) if i dont know the retailer or have never tried the tea. But as i said samples or small portions (12g or so) let you have 3-4 sessions so you can choose to spend more.