Typically if it's used it's instantly depreciated 50%. But these are extraordinary times, and the used market is quite strong. That also applies to cars and housing. You can look on eBay for recently sold items and see what they got. But I think the used market is going to soften, at least with bikes. Supply is starting (but creeping) to pick up. You can always price a bit higher and have an 'OBO' attitude, but never publish that attitude. But right now, high end if very good condition, I would list closer to 70% of retail and be somewhat firm. Trying to procure high end forks, cranks, etc is hard right now, everything is going towards full bikes, which helps the used bike market.