Any modifications from stock rarely help resale value of a motorcycle one iota. If anything they hurt the value; used buyers are looking for the least-molested, closest to stock bike in the best condition they can find.
Seems like all that modifications can do when selling a bike is either speed up the sale process (if they are popular mods and you find a buyer who wants the same things), or slow down the sale process (if they are strange mods that aren't appreciated by anyone but you).
A $3500 motorcycle + $500 exhaust + $250 in aux lighting + $300 custom seat = $3500 used motorcycle for sale.
That's why as a seller, you make out best by removing all mods you can as you're selling the bike, and parting them out separately to get at least some return on them. I love the craigslist ads where some clueless newbie adds up every dollar they've ever spent on the bike, including maintenance, (heck, why not gas?), puts a huge total at the bottom, and expects someone to knock on their door and hand them a huge check that exactly equals everything they've ever spent. A fun corollary is that same type of buyer who managed to purchase a $9k motorcycle for $14K by not looking at anything past the $99/month initial payments, and expects someone else to dig them out of that hole with a $14K check out of the goodness of their hearts.
