There are not infinite caps, some sources are giving way too many out and leaving nothing in the system. That needs fixing.
So you're trying to make EVERY resource (except encounters it would seem) a drainable resource?
And again, what would be the alternative resource to the slave run repeatable quest? Because, honestly, anything else would be wrong.
reasons:
1. It is how slavers can afford mercenaries. (hell you pretty much tied the two together with steel instead of yarn this era)
2. It doesn't make sense to be paid anything else... maybe jet, maybe. but still, not JUST jet.
3. Trying to make only resources for caps scrounging encounters and moving boxes and shovelling shit? God please no, that's all boring (maybe encounters not so much but it's still mindless grinding).
Perhaps! you could mix caps and jet together as a reward. this way we still get our caps, but it is sensible we're given jet as we are slavers and control the slaves by drug addiction.