Or you can look at it this way.........you have to pay the tax either way, so it's no difference buying direct from the seller or buying from a dealer...Never heard of that. So you are having the new buyer basically buy the sled from the dealership? If so that kind of de-rates the purpose of buying used. AKA saving money on taxes if you know what I mean. If was buying a used sled and had to pay full tax on it I'd say thanks but no thanks.
I will say this, I have a sales tax license that I will not jeopardize for someone else to save a couple bucks on a sled they are buying from me.....and NY has started checking in on this type of stuff recently. Whether buying direct from me or thru the dealer, we agree on the price and I make sure the buyer knows that price is the price going on the sales paperwork so they are aware from the get go......