I've had good luck with roofers taking after hours and weekend work. You buy the materials; they install. Three years ago in B/CS I paid $14 a square for labor. Included installation of flashing and felt.
I had bought the shingles and was on the roof rolling out the felt. Jose and his buddy pulled up and asked if I needed some roofers. Naw, I'm doing it myself. Jose says, "how about $14 bucks a square?" I say, "When can you start?"
They finished the next day.
If you have to tear off and dispose of the old material, you have additional costs, obviously. And need a truck and will pay a disposal fee.
These guys aren't bonded and when they leave the roof is yours but you're paying for their labor only; not the overhead of a roofing company.
I have no complaints and paid a third (or less) than I would have paid a roofing company.
If you need the comfort of dealing with a business, your quoted prices are in the reasonable range.
If you don't need that comfort level and want to save some significant bucks, Juan, Jose and Roberto can do it in a weekend. You just have to find them.
Se habla Espanol, of course.