The very little pitch is a possible savings right there. Shingles are not meant for low pitch roof, you need roll roofing and that is even cheaper (and faster) than shingles, Measure the 'run' (width of roof) then find the 'rise' (how much higher the high point of the roof is above the low point). The lumber yard can tell you if you need roll or shingle. They will also give you a list plus cost of everything you need. At least they will if you shop real lumber yards, not the big box stores. You will need about 4 1/2 square of roofing material (including felt either 30 lb or 50lb), nails, flashing. Should come out in the $160-$200 range all up. Full instructions on application from deck preparation to how to lay the felt to nailing is included on the roofing wrap.
Harry K