I purchased a Selle saddle off of Amazon a couple of years ago. Sold by a third party vendor but shipped by Amazon. It’s been great and from all I can tell it appears to be the real deal. I’ve got about 10k miles on it now.
Almost everything I buy on Amazon is offered with free returns which I’m not shy about using. If it is something I question and does not offer free returns I usually pass unless it it a very inexpensive item. Their return policy offers full buyer protection to inspect the item and if you don’t like it just send it back at no cost. And Amazon has been very good about refunding my money quickly, usually within a few hours after I drop it off at the UPS store.