Most of the Nada values on 90's models in that length are less than $2,000, which if it's well kept, is worth more than that to most people selling them. The price of the aluminum alone is probably worth that, and if someone has put work into it, than it's worth more to them.
Realistically, a real value is what a willing buyer will pay a mutually agreed upon price to a willing seller. As a buyer you only need one seller to agree on a price for a unit you want. The real value of the unit is what you are willing to pay, and they are willing to sell it for.
Before I bought my MH, I looked for toy boxes. For me, the prices people were asking, was more than I was willing to pay. So I changed to broaden my search to find something that would both meet my needs and was of value to me. I was open to many options, but would have had to increase my value of a Toy box if that was what I was set on. If that's what they're selling for, that's what they're really worth. I searched a 500 mile radius of my location, and still couldn't find something I felt was worth what they were asking. The NADA value of Toy Boxes was thousands more than what I was finding in the Texas area. There could have been units in another state where NADA values were closer to what owners of Toy Boxes were asking, but I didn't find them. I know here in Texas you will get a lot more than NADA value for a Pick up than you will in some other states. Most everyone I know here owns at least one PU. So location may matter as well.