We have both "per inch" and "per hour" available in our area. The "per inch" does all the work for you and delivers a finished product. The other involves you renting a either a manual or a computerized machine. You sew on the zipper yourself for both. For the manual, you can use either a pantograph or free motion. For the computerized, you choose the pattern. The employee is there to help as needed. There is also a flat rate thread charge, depending on whether the pattern is considered light/medium/heavy. Average charge for a lap sized quilt is about $50. The computerized machine is booked solid Jun-Jan. Don't think the manual one is booked as much. Guess the difference is whether your quilt is a show piece or not.
Personally, I like the feeling of completing an entire quilt myself and the rent option fills that need for me. I don't however like paying a flat rate thread charge. The charge for one quilt pays for the entire large cone of thread.
Will follow this thread closely as I have also wondered about the profitability of buying a LA.