I buy most of my mods used. So many people sell barely used parts because they want to try something different or upgrade to a new car. I also sell my cars stock and part-out the mods separately. It's still expensive but the cost is minimized with this approach. I have been lucky enough to sell some parts for the same price I paid for them.
'13 M3 - Silverstone II - Sold
'04 M3 - Jet Black - BBS E88, KW Clubsports