"A superb paint job for my family room and kitchen area. It's like I have a new home. I was so sick of the dull colors I had on the walls for several years. What a wonderful experience to see how new my 15 year old home has a wonderful, bright, clean look. Then, the next job was countertops of granite in my out-of-date kitchen. Wow! It is a brand new kitchen - everything I ever wanted. M. Guerrero and his employees did a masterpiece of a job on my new, beautiful countertops. I am extremely happy with the work. These men are absolute experts in their field. I will be calling on them, again, in the future."
Take for example, I charge 1.75 sq foot for 10x10 room with 8 foot ceilings. By my calculations this would cost $175 with floor space sq foot, but with you method, it would cost $576.00 That is outrageous. Of course I didn't subtract the windows and doors, which is another thing that makes no sense. Cutting in around those windows takes more time, then just rolling a wall.
You might pay an additional $1 to $5 per square foot for optional repairs and updates. Consider having your molding, trim and baseboards checked while you have a professional in your home. This might be a good time to upgrade or repair any cracks, warps or other issues. Pros can usually touch up or replace these items for an affordable rate, and they may even package such fixups with your project.