I feel it honestly depends a lot on experience of the candidate(s) chosen. Need someone with a college degree? That may cost more.
You might be able to get a startup for little more than $10-$15 an hour. But to hire a seasoned artist/musician with industry experience, could very well run $35-$50+ an hour.
If you can only offer a lower price... it may also provide incentive if they can do the work from the comfort of their own home.
Lastly, for small jobs, you might also look at something like Fiverr, and browse the really high-rated artists/musicians with impressive portfolios.
Just some food for thought / tips.