Checked around at the used inventory for the dealers in my area and found three '17 FLSTC models for sale:
950 miles for $19.980
10K miles for $18,495
2.7K miles for $19,094
These are dealer prices and I assume based on "book" value but actual "street" value is probably about $2K less. So, the OP could advertise the bike for say $14,950 and be prepared to let it go for $500 to $1000 less. So, assume it takes six months to sell, add six months of payments to the difference between $15K and $13.75K and make the decision on whether to take that hit or the $4K hit from the re-seller. Of course, there is always the chance that the bike could still be sitting in the garage in six months but you are a better judge of how likely that is possible. Time to fish or cut bait; procrastination is not advisable.