How much per sq/ft to paint room?
I don't know about Mass. but a good painter figures in the size of the room, condition of the walls, and the number of doors and windows. Each door and window will slow the painter down because of the time it takes to cut in around it.
A good painter will rarely if ever quote one coat. Its usually two coats or two coats plus a primer coat. And they will not use cheap paint. They figure it all up front, not to make extra $$ off you, but to avoid call backs. IF he does one coat and you aren't happy with it, you will not forget you only wanted to pay for one coat.
Best bet - get three quotes and pick the middle one.
Many residential painters can and will vary greatly in price and probably do not calculate their estimates based on sq footages, but rather ceiling heights, amount of trim and whether or not they can spray the majority of the work-- how many different colors on different walls.
In Texas, the average price of painting a room (regular size and normal amount of trim)- with one wall latex color, ceiling white, and one different enamel trim color would be about 350 dollars. (for walls, ceiling, and trim).
If someone just wants to get their trim replaced, painted or stained, we usually charge about a dollar per linear foot to replace and a dollar to paint or stain-- plus the cost of the wood. If a wall with 8' ceilings needs to be painted-- 12-16 ft wide-- usually a hundred dollars per wall if the customer does not want the whole room done.
Cabinets are a whole different story and totally depends on the job