your car IS unique. But a large part of that uniqueness is the age/miles. Its like a cellared bottle of wine. You've proved you can cellar it. You could sell this one, and buy something else and start the cellaring process anew. Or buy something that doesn't need cellaring and you can enjoy every day.
Honestly, if someone offered me that much for your car, i'd probably cry a little, but do it.
Very good point Grinder.