Yes, I'm back with another Yugoloth question.
So Yugoloths are known as mercenaries, primarily for Devils in the Blood War but also for powerful mortals and other beings, if the price is right. My question is, what do you pay them with?
I've seen it suggested that they take souls. What would they do with them though, since they can't make any more Yugoloths? It says in the MM that they need souls to power a ritual to bring one of them back if they were killed on Gehenna, but I don't know if this occurs often enough to be worth it to them. Furthermore, how do non-Devils acquire souls for trade besides their own?
The other option is gold and other kinds of material wealth. What the hell would Yugoloths do with those? I could see them hoarding gold and material wealth purely out of their cosmic Neutral Evil nature, but it seems like a waste, and that they would be smart enough to put gold to some use. Buying powerful magic items or equipment seems redundant since they're already decently powerful fiends.
TL;DR — What forms of payment do Yugoloths accept and how do they make use of them afterwards?