I honestly never try to factor in any resale value into my upgrades.
I don't care..
if I want to salvage any useful items I have installed?
I can spend a few bucks and have my guys retrieve my items to be reinstalled into a newer rig if I so desire..
Or can give them to the buyer as incentive.
Case in point.
I had a 28ft tt with 575 watts solar @ 12 volts with a 3k watt xantrex marine modified sine wave inverter/charger.
I knew I was going to go another way in the new rig . So I gave it up..
Alot of give and take as you get smarter I always say. ;)