Then you need to have a fixed material cost, eg with NPCs buying stuff.
At this point, you can also have fixed cost for all things. Then YES you can have meaningful collateralized loans.
FWIW that was already done when you had excess of mats in places where it was difficult to move the mats. Build ship, insure it, explode it : you are literally paid money for destruction. This happened when some moon goo had minerals in them, don’t know if it’s still a thing. (insurance value is based on the materials)
Also the “item material cost” depends on a lot of things. base BPO ? ME10 BPO ? ME10+rigged structure in FW area ? ATM there is no intrinsic minimal mat required (even though there is practically one) so this kind of process could lead to later abuse. That’s actually why I made that proposal : Some Ideas of mine - #7 by stefnia_Freir