Need advice on contractor's quote for completed roof and windows

[Crystal Em]

We're working on our first project, a SFH flip in Houston, TX.

Our contractor presented us with a price list tallying the work he's done so far. The two largest items being replacing some windows and reframing the roof of a pre-existing 400 sq. ft. back addition to the house. 

He is quoting $3000 in labor and materials for replacing 10 windows (including one small window over the sink in the kitchen) with standard vinyl replacement windows. 

For the roof work, he is quoting us $8000 in labor and materials for replacing the previous flat roof, reframing it to match the pitch of the rest of the house, and raising the ceiling inside the addition to match the 8' ceiling height of the main house. 

What do you guys think of these prices? They sound like a lot to us, particularly for the roof work since it's only 400 sq. ft., but being newbies we have no frame of reference. Maybe we're actually getting a steal. 

I've added some pictures to give a clearer understanding of the work. 

[Michael Blass]

I am a contractor in Ohio, and those prices don't look out of line to me. Until I saw the size of the roof, frankly, I was thinking that the $8000 price tag was too low. I am assuming they are doing the inside work also (drywall, paint, etc.) to finish it off?  Regarding windows-you are at $300 per hole. That's pretty close to what we charge up here. I can't speak to costs in Houston vs Ohio, but I am in an economically depressed rust-belt region, so I would think Houston prices would be higher. Notwithstanding the fact that in the contracting business you can almost always find someone to work for less money, (then the real question becomes what will that lower-priced contractor actually cost you in terms of quality, deadlines, hassles, etc.) from the information you have provided, I think your costs are reasonable. Good luck!