Dealer and owner asking prices are often much higher than they will settle for.
If the Winnie is "perfect", it is still 11 years old and AC unit, fridge, furnace and slide mechanisms ,batteries ,etc., may need repairs/replacements in near future. If tires are over 5 years old by date codes, they will need to be replaced for your safety. Drive train, brake system and suspension should be inspected by a pro truck mechanic and you should get an itemized list of rand repairs needed with parts and labor estimates. If near perfect, it may be worth $20K.