Yeah, yeah, yeah. Standard RV sales talk. Sure, he would rather sell the Santara for cash. And you would rather sell for cash than trade it in. But both of you are in the real world, so a trade is part of doing business here. Don't let his tears worry you - if he really didn't want it at all, he would say "I can't take your rig in trade".
NADA lists 99 Santara's, the larger ones anyway, at $35-$40 grand. Even the diesel is in that range. NADA RV prices are higher than private sales bring (a lot higher!) but in some areas may be close to real dealer pricing. PA seems to have high RV prices, from what I have seen and heard here on this forum and elsewhere, so maybe he's in the ball park for your area. If so, I would be inclined to look elsewhere because you can get better built coaches for that money in other markets, where there are a lot of RVs.
So if you are comfortable that your rig is really worth only $5000 in trade, maybe the deal is OK. You can expect no more than low wholesale book value for yours on a trade - anything else you get for it is essentially a "discount", money you could have gotten off as a discount if you had no trade.
A 7000 watt genset is big for one of these rigs - is this the 35 or 37 foot diesel model? Or is it on a Ford gas chassis.