When we traded in our last TT (only one I've ever traded), the dealer wanted me to remove the Steadyfast system and flat screen TV as they weren't included with the original. I took out the TV, but told them there'd be holes left if I took off the Steadyfast.
Dealers are really focused on buying and selling units that are just like they are straight from the factory. That's why NADA, etc. don't give much value to add-on things. As for packages, if you look at the online versions of the NADA guide for 2016 (
http://www.nadaguides.com/RVs/2016/Keystone-RV), there's no Legacy, but there is for 2017. You'd have to add the individual upgrades instead to get anything for them, but that's a bit beyond a typical salesman's capability . .