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.
_{Basic labor to paint home with favorable site conditions. Prep up to 3 hr per 100 SF - clean, scrape, sand and patch up to 4 defects per 100 SF. Caulk gaps and spot prime. Roll / brush 2 coats of paint over lightly textured ceiling/walls. Paint up to 2 doors and door trim per room. Includes planning, equipment and material acquisition, area preparation and protection, setup and cleanup. 129 square feet $97.99 $132.56}

"I had Sam and his team come in to repaint our kitchen cabinets that were originally a dark wood stain. He cleaned, sanded, primed, and put on 2 coats of sheer white on both the doors and frames of the cabinet and they came out great. The kitchen is much brighter and even up close it is hard to tell that the original cabinets were not white. They were prompt and very communicative over the phone. We may soon hire them back to paint the kitchen next."