Looking at those NADA prices, I see there are often only differences of two or three hundred dollars between the same or similar models manufactured 10 years apart. This brings to mind that condition is often much more important than age (within reason).
For example, a trailer that has even a small amount of water damage from leaks is probably worth many hundreds of dollars less than a similar one that's solid and has always been dry. The level of maintenance may make a lot of difference. The amount of upgrading is important--a trailer with a new Fantastic Fan, improvements to the seals all over the trailer, new fabric on the awning, a replaced and upgraded converter, upgrades to the refrigerator fan(s), better drain accessories, added solar panel recharging system, better battery setups, replacement LED light bulbs, new tires, and so on can make a huge difference in value. In addition to the obvious like cleanliness and overall eye appeal.
There are trailers easily worth twice some of the figures in the NADA guides, or more. There are others that you probably should not accept even if someone is willing to pay you to take their disaster off their hands.
You really should look at what's on the market, note advantages of your unit compared to what you find to be average condition of other available trailers of similar age and type, and be prepared to do an honest selling job of features and condition points you believe are above average.
You will probably also take into consideration how much trouble you want to go to, to maximize your selling price, or if you want to price it low to unload it in a hurry and move on to other things. Sometimes, an extra $100 in return will cost you over $100 in time and/or effort.
Sorry if this doesn't give you specific advice, but hopefully may provide some food for thought when determining your pricing approach.
1999 22L Classic
2008 Toyota 4Runner V6