I don't know if it is fair to say you are way off base or not. Keep in mind, low retail 18k, average 22k, suggested 28k is retail. Wholesale is substantially less. Depending on condition, 16k retail for your TC could be reasonable but wholesale much less.
I have never had much confidence in NADA. I guess it is better than nothing. The same is true with Kelly Blue Book. I see them as nothing but a very loose guide, primarily used by dealers in RVs and other vehicles.
I do not buy new RVs or vehicles, and have not for over fifty years. With rough numbers, I look at your TC cost, about 30,000 new, three years later worth 20,000. That is $3000 per year cost, minus sales tax. My mind cannot justify that cost. But, that is just me. If you look at the dealers figures, at 31,000 new, worth 11,000 in three years, almost $7,000 per year.
It is fine if you have and are willing to spend the money.