I think part of this happens because the tea shops themselves may not even know the difference. Case in point, for one Chinese tea seller on eBay with a quite large shop, a “white” Silver Needles was actually a green tea imitation. It looked exactly the same as a white Silver Needles, but with a green tint!
For U.S. buyers: on eBay, for 50g to 100g of white tea, a usual price seems to be in the range of $10-20 USD. Some special aged or premium quality white teas will cost more than this, naturally. But if you are paying significantly less than in this range, it is very likely that you are getting scammed with fake or low quality tea. If you find a reputable Chinese supplier on eBay, then you can have a reliable source of quality tea. Look carefully for a past history of good transactions, and also look for detailed photos of the actual tea leaves.
