Most professional longarm quilters charge by the sq. inch. Depending on competition in your area it varies by region of the US. Base prices can range from $.01 to $.03 per sq. inch and then go upward from there. Charges for thread and bobbins are normal charges along with any other charges for any services such as suppling batting, any repairs the have to made to your friends quilt, binding if asked for. Quilting charge alone for a quilt say 80"X100" at $.01 per square inch would be $80.00 not including supplies or any additional services, and $.01 is a really good rate and there would have to be a lot of competition in your area for a rate that low.