Regarding price, You didn't mention the model or options so can't give you a good answer. Run it through the NADA guide on line. This will at least give you a benchmark, and then you can search for similar and see what they're selling for. It does sound a bit high to me though.
Other than obvious things in general to look out for with any RV, I'd like to give you some pointers about what to look out for specifically with the KZ brand, but I can't think of anything where I've had any trouble with our Inferno. We're very happy with it so far.
Like you, we were also looking at Fuzions and Raptors and the sheer lack of complaints on the KZ is what drove us in that direction. I've called the factory a few times with questions (not problems). Every time, I talked to a real person who was nice, knowledgeable, and who had alot of time/experience working for KZ. What a breath of fresh air that is...
I have heard that many toyhaulers (KZ included) have had problems with the lift springs on the ramp door actually breaking the structure of the door just above the hinge. You might check that out...
I'm struggling to think of anything else, but if I do I'll come back and let you know.