The 'trade in' price will always be lower than market retail price because the dealer has to make a profit to stay in business. He also calculates the time cost to prep it for sale, repairs needed and estimates the time he will have his money tied up in it before it sells. That is all part of being in business as he has to sell it for MORE that his cost plus overhead including business license, insurance, taxes, employees, etc.
Selling it yourself means you have to store it, advertise it and put up with the tire kickers, hagglers, whiners and those who want a warranty.
There are pros and cons to each aspect ~ your choice.
2012 Fun Finder XT 276 Toy Hauler & Harley Davidson Ultra Classic with Condor wheel chock
2014 Dodge Ram 2500 AT 4X4 Crew Cab 6.4 L Hemi, 373 gears, tow package, Rambox option, Revolver X2 tonneau cover, Equal-I-zer anti-sway hitch.