And $20/hr is *not $20/hr to the quilter. Out of that she has to pay self-employment tax (15%) in addition to regular income taxes, not to mention insurance, maintenance, office expenses, utilities, etc. I think I read recently that the quilter is likely to end up with half of that after all the expenses. $10/hr is not a lot to make for skilled work.
I was self-employed as a graphic designer for 13 years. By the time I left the business ten years ago, I was charging $65/hr and not getting rich. I was also as busy as I could get without hiring others. There's a lot of unbillable time, and I would think that holds for quilters as well.