I'm not sure what cut Etsy takes, but some places take quite a bit so that's definitely something to look into.
I've bought a couple interchangeable needle cases (love them!) from Etsy.
ETA: Okay, I looked up info which you can find as well if you register on the site. There is a listing fee and a transaction fee which doesn't include shipping or taxes. The numbers look relatively small, but it'll all add to your price or cut your bottom line. I'm not trying to discourage you just want you to be aware of everything.