So, "High Retail" is in the $9,000 range. If one sells the vehicle to a collector, would he/she pay as much as $20,000? It's possible.
Not bloody likely. Even if your Jeep was worth $20,000, which it obviously isn't, a collector would not pay that price for it. Considering the fact that collectors have much more extensive knowledge of Jeeps than you do, plus the fact that they also have access to the same report from NADA, you'd be lucky to get more than a few thousand out of a collector, or anyone else for that matter. What you have is not a collector's item. What you have is an old vehicle.
Now you're saying your Jeep lists at "High Retail", but I don't believe you have an understanding of the condition a vehicle needs to be in to attain the "High Retail" value. Just because it has original paint, body, interior, etc., does not mean it's in perfect, or pristine, shape. In order to be in that shape, it would have to have been stored in a climate controlled building and regularly maintained, rarely driven, and not have a speck of rust anywhere. The paint would have to look like showroom floor quality, and not have even so much as a slight blemish anywhere. Even if you have no dents or dings, if it has been driven outside, it will most likey have blemishes in the paint, and definitely have rust, if even on the frame and bare metal parts. At best, for the age, you might have a vehicle in "fair" condition. Discount that if there is any sign of fluid leakage from anywhere on the vehicle, signs of wear on the movable parts, etc. Unless you can present the vehicle to me personally so I can lay eyes and hands on it, I cannot verify what you say is true.
Bottom line: If you want to sell it, put a $2000 tag on it and take whatever offer you can get. If you don't want to sell it, hang on to it and keep trying to convince people that it's worth $20,000. Just not people who have anything more than the slightest of intelligence, otherwise you are wasting your breath and their time.