If you've sold an existing head unit and re-couped some costs after using it, that's pretty much your "discount". It's what I and a lot of others have done. Sold (preferably) or returned (usually less $) our existing Karoo 1 (or other) units to help fund. There are not too many bike bits where you get as much of a return as I got on my Karoo 1 after 2+ years of pretty heavy use. Guessing my bikes and wheels haven't retained well over 50% of their original value.