I've never had one quilted by a professional but I have overheard others that have talking (we have 3 LAQ in the area) and we don't expect to pay under $100. Their skill, time, etc. is worth it. Queen size may be over $200 depending on the quilting pattern.
My DH is a self employed contractor...there is no way he would belittle his ability and charge a price that doesn't even pay for gas, why would we (you) charge so little for your work. Please look into this fully, join that yahoo group for professionals that someone mentioned, and don't let the quilters that want you to quilt their work push you around, just because the other lady charged too little.
Our quilt shop lets you rent their Tin Lizzie (once you've taken a class with them to prove you know what you are doing, can't wreck the machine!!!!) $10 load up fee and then $20/hour. You supply your thread,needle, etc.