That sounds like a lot to me. I just took an arbitrary measurement for a king at 120" square and based on a $150 price quote they are charging you a bit over a penny per s/i for basting. Many LAQ charge that for an all over meander. I have heard some LAQ only charge about $50 for basting. I've never basted a quilt for someone but I would think 1/2 a cent to 1/3 of a cent per s/i would be more in line for basting, depending on your area.
Gertz, the original poster is most likely handquilting her quilt in a lap hoop which requires basting the sandwich. Rather than basting it herself she is seeking the services of a LAQ to sandwich and baste the quilt for her.