For the dealer or a private seller, the problem is the same; their money is tied up until they sell the unit.
The dealer want to buying low enough for a quick markup and sale. It costs the dealer to have the TT sit in inventory.
The private seller usually can wait, there is no immediate pressure to "turn over the product" it is paid for and is not costing much to keep.
The dealer has overhead and profit to cover, the private seller does not. The dealer is not bothered by strange people coming over to take a look, or no shows or haggling over the price, some folks are.
Personally, if the dealer can sell me the TT I want at the price I want it, I do not care how much or how little he can get for my old TT. If he cannot I keep looking.
Good Luck