I don't know about quilting, but in other arts, it depends on what the vendor does for you. I'm sorry but I don't have time to go in details for you... time is of the essence with my LO soooo here is what I've seen 30% if you're lucky and as high as 60%. Most folks I know are around 40-50%. You have to think that if it's a storefront, you are using rental space, they advertise for you, they have a client base, etc. It's like in the publishing business; if you publish your book, it's cheaper but distribution is a bear; however, if you can find a publisher, which is hard, then distribution is a breeze, but less money possibly.
GL :)