Just give them back to the attendant when you are done with them. He refunds a percentage of the cost.

OK! I think I have nailed what quality lock is needed for reps here. It's not related to what lock you can get with a copper pick and no lores.
It's instead based on what you need to get a rep when picking. To get a picking rep, I need to use a Myklian pick or better, no lores, and have a lock
in the low 600s at minimum.

So, I made a lock assembly at -630, and got a rep. -620 and -610 were the same. When I got down to -600, I got no rep.
Mystery solved ... maybe.