if you want $15k for it, put it back in the garage and wait 15-20 more years. Then you’ll get some value like that from it.
There is a guy in PA with a 1997 Bonneville SSEi 40th anniversary edition (one of 637) with only 155 miles on it who is looking for $30k/bo who is in the same boat. and I would give that one a better chance of getting the cash sooner.