Ahhh... the age old question: old vs new.
In our case the old camper kept springing leaks no matter how often we inspected and resealed it - each season we'd find something new. Then there was that front window that they used to put in them - while a nice feature it was more of a PITA than "nice to have".
While everything still worked in the end we thought we'd never be rid of the musty+mold smell from the leaks, we were loosing confidence in navigating the steps in/out and lastly we were unsure how much longer we'd be willing to make the climb into the sleeping area of the old non-basement model. (besides we really wanted face-2-face booth seating)
The "book" on the old one was a mere ~$2000 in perfect condition, we got a small fraction of that on 'trade in'. The markup on new RV's is astronomical and great savings can be had on units a few or more years old. While we were unable to find a used unit to our liking and realize any savings, we are more than happy with our choice of replacement.