If you can post a picture of the quilt top, it would be easier for us to provide suggestions. Also, what are your plans for the quilt? Will you be entering it in any judged shows? Using it as a nightly bed cover? Or, perhaps as a bed cover during the day only?
Generally speaking, the larger the quilt is, the more expensive it will be. The more custom the quilting, the more expensive it will be. The more dense the quilting, the more expensive it will be. The more thread color changes, the more expensive it will be. But these are just general rules of thumb.