Unfortunately, the days of $2 per yard fabric and 50 cent thread are gone. Most of the fabric I purchase runs about $10 per yard before taxes. More for nice backing! Much of it is not available locally because no one has local access to infinite selections so that means there are also the inevitable shipping charges.
I try to keep my prices about half that of city boutiques. I can compromise on the cost of my labor, but will not compromise on the quality of materials.
Naturally, the larger your quilt, the higher the price. As you can imagine, while piecing is not so unmanageable, the quilting process on a queen or king size piece can be quite a feat for a person with only 2 hands and 2 arms to work with.
This gal would have no problems but as you can see, she is occupied with more important tasks.
But there is no rule that says your quilt has to cover your entire bed so if you have a king size bed but cannot afford a king size quilt, consider getting a full / double or queen quilt top.
Also, bear in mind that it takes some time to create your quilt so I can always work out arrangements to pay as we go along in the process. Your first payment can cover the cost of fabric and piecing; your second, the cost of batting and backing; then finally the quilting and shipping. And we can move at a pace that works with your budget.