I buy a whole lot of my fabric on sale so I have a good stash to pull from so it's really hard to say. I think some of my quilts have cost between $100 to $150 for all the fabric and batting. I have made a whole bunch of scrap quilts out of the leftovers though so that brings the cost way down.
I do have some quilts that cost a whole lot more because they were BOM bought at full price at the LQS. I bought them because I liked the pattern and to help support the LQS.