I know different scenarios require different prices, Generally speaking i think its safe to say that the price you can sell it on at depreciates at different rates and those rates can be any number of things(and are worth logging just like to do a car, receipts and all) as soon as you use it on your bike, and then over time continues to fall in potential sale price until you hit a 'plateau' and from then on the integrity of the part as far as the buyer is concerned is regulated by the user with maintenance and what not.
My point is that although you may have maintained your bike and spent money with much needed pre-service sale maintenence, i think most peoples prices are a little on the adventurous side when it comes to full build sales. Ultimately a very used bike that cost £1000 to build won't cost £750 3 years later. The warranty will have gone, the bike has been used and cleaned any number of times. Yes money has been spent on it, yes it's back up to working order but come on……..Are you serious?
People use these sites to get a bargin. Lets make it happen.