I just recently learned of this site. I think it could do very well to refer them to it so they could get an idea of what quilters charge for what kind of work.
On it they have everything from placemats to California Kings and IMNSHO, I believe they are quite fair.
If you don't wish to refer them, it could do well to take a look there yourself. I think so often we sell ourselves very less than what we should.
The site is based in Canada (hence the .CA suffix in the web address), but the clear majority of quilts listed are from the U.S. Interesting place to visit from time to time.
Go to:
http://www.quiltsforsale.ca/
~Jo