There are so many people trying to make a quick buck in the detailing sector and getting their products made by one of a few factories who are offering minimum order levels and own label.
The big problem is, these are part time lads having a go, but have no product liability insurance, 'customer service' is by mobile or e-mail (ie when it suits them) and the same products are sold, as has been mentioned, at wildly different prices.
If the product goes wrong, you're on your own.
Frankly, if you have a decent car, I wouldn't take the risk. You wouldn't with oil, brake pads or filters so not a great idea with bodywork products.
However, if you have a 2 grand Corsa you've got nothing to lose....