A lot of it will depend if they have the same model still new on the lot or not! My folks traded theirs a 2012 grey wolf something or another for a columbus 5er and only got cut $1,500. When we tried to trade our which we bought a few months after their first one ( a grey wolf 26dbh) we were going to get socked $7,000 like you said but they had about 8 of the same thing already on their lot!
Fortunately but not we had all sorts of issues with ours, some of which I felt jeopardized the safety while towing the unit. With said issues they gave us $5,000 more for the one we traded and $5,000 off the current one we have... we sort of lucked out in our trade...
Sad thing is, I told them I didn't want the trailer back due to the issues I was having with the previous one, axle alignment was WAY off due to the brackets being welded in wrong location, and a number of others. The dealer sold the trailer before I even had time to get all of my stuff out of the old one and into the new one at their lot! They said they notified the new owner of the issues, but I am highly doubting that!
TV- 2015 Ram 2500 CCLB 6.7 Cummins 3.42 gears
Camper - 2015 Saber 322BHTS