Competitive rates are usually structured to the individual task. A phone call to discuss your particular needs will assure you of an accurate price.
Hourly rates are my usual form of billing, as we both are assured of neither an over nor an under charge. I believe in fair pricing on all of my work. Billing is in increments of 15 minutes with a minimum of three (3) hours.
There are instances when I will prepare a firm quotation. These usually include tasks that I have enough experience with to know how many hours are involved for it's completion. Field repairs and upgrades are always billed on a time and material basis, as there are too many unknowns for a firm price to be quoted.