I've seen two different 7 Up convertibles over the last year. There is one about a half mile from my house and I saw another at a car show that was low mileage. He was trying to sell for $6k.
Yes, unfortunately they aren't viewed as a collector car, price wise. I've seen run of the mill, modded and whooped GT's and LX's bring the same if not more than an equivalent 7.
Six years ago before mine was mothballed, it rarely was given a second look. Most don't even get the 7-Up reference (and it takes too long to explain :-/ ). Now, it's hard to stop for gas and not get a quick passing positive comment from somebody. And mine's not nice, honestly. Lack of indoor storage space around here just eats 'em up, covered or not. White top and white interiors are not for the OCD minded .
I'd like to get some pics of this one together beside Dad's Tiger in my avatar very shortly, when the leaves color up a bit more. Been wanting to do that for more than a few years now.