The idea is to offer a crown reward for each usable item picked up but not used at the end of a mission.
Ideally this would challenge players to use as few items as possible with a sliding price reward
For example:
100 cr-health capsules, remedy capsules
50 cr-summonables (mecha, recon, turret, bombs, ect)
25 cr-vials and shields
The purpose of this would only be to make levels harder as players would be encouraged to not use the usables they acquire in order to later trade then back in; it could be pitched as Haven buying back supplies gathered from the clockworks or something.