The nut itself might only cost $5, but it will cost more than that to get it properly slotted and fitted to your bass. I would guess maybe $40-50 total. Maybe less if you're lucky.
However, the good news is that if it's done right, it's probably something you'll only have to get done once. If you get a nut made out of a good solid material and it's attached right (which means, not too much glue---you should be able to remove a nut without breaking it) it should last the life of your instrument.
However, the good news is that if it's done right, it's probably something you'll only have to get done once. If you get a nut made out of a good solid material and it's attached right (which means, not too much glue---you should be able to remove a nut without breaking it) it should last the life of your instrument.