The cost could depend:
1. Where and when you purchase your material
2. The size of the quilt that you are considering quilting
3. The quality of fabric you choose to you use
4. Whether you use recycled fabrics (t-shirts, old clothes recut) to add to the newly purchased fabrics
5. Whether you are handquilting or machine quilting/ this could determine the amount amount and colors of thread
6. Whether you are going to outsource the quilting of the quilt once you complete the top.