Well, the fact is your 1998 isn't worth much on the open market, especially since the typical trade-in offer is essentially low-wholesale. Since $16k-$20k is all he can hope to re-sell your coach for, the $16000 he talked about first had to assume a discount off the asking price on the 2005.
If you have a nice clean 1998, your best bet is to sell privately and then go negotiate a cash deal on the rig you want.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC