Generally, it will take a minimum of two gallons of paint to cover a room. At the highest end, paint will cost anywhere between $30 and $60 per gallon and come in three different finishes: flat, semi-gloss or high-gloss. Flat finishes are the least shiny and are best suited for areas requiring frequent cleaning. Semi-gloss finishes are a bit shiny but can also be easily cleaned. A high-gloss finish is stain-resistant and easy to clean. Traditionally, living rooms should be painted with a flat finish to allow the paint to stand out. Glossy finishes should be reserved for hallways, and a semi-gloss is best suited for trim. Invest in pre-primed paint whenever possible. This cuts down on time by combining the layering process. Almost any paint job will require a primer, which will cost anywhere from $7 to $15 per can. Primer helps the paint to stand out against the underlayer of paint it's covering, especially if the new paint is lighter than the old coat. You will need at least two cans of primer, if not more, to cover one wall. Here are some paint brands and their average price per gallon:

Home Painter Co

Hello, I have a sad situation to share -- a friend of mine who is a very good painter, experienced too, fell off a tall ladder that did not have "boots" on it. (I've never seen those.) Anyway, do you think he should have asked for boots before painting? Possibly it was a situation where he was shy to ask because he wanted the job... (I don't know all the details.)
First off, the picture on the top THAT IS A HOME OWNERS PAINT JOB. If you here a school kid or your neighbor, this is what you get. I was a painting contractor for the better part of 40 years and never saw a PAINTER (even the worst painter) leave a mess like that. Maybe the electrician or the carpenter but, that is not something a painter could even do if they tried.
I did go with the highest bidder and it did not matter. They did a shoddy job and threatened to take me to court when I pointed out mistakes that they made based on their work standards stated on the quote. I have not paid them yet, just filed a complaint with the BBB. No money down asked, no contract signed. The boss stated I have to high of expectations just because I live in a 121 year old house!
Consider purchasing supplies personally to save money. Ask the painter for a bid that separates labor and materials. Then explain that you'll purchase the materials and ask for a list of exactly what will be needed to complete the job. Caulking, for example, is an extra supply commonly used to fill any cracks or damaged areas in your walls -- and one that might be overlooked in an incomplete list.
There are cases where apartment complexes allow you to choose from a color wheel of neutral hues before you move in. Some charge a fee for calling in a painter to do the walls, while others offer new paint as a benefit of moving in. If you're not a fan of neutral colors, consider looking for an apartment that allows you to paint the walls a more expressive tone. Otherwise you can invest in boldly colored furniture and posters.

IF the average cost is $1700 to paint an interior, then that means the cost of paint is approx. $200 (12% of the job).  Or better said 5 gallons of paint (if the average cost is $40 retail).  The average room takes 1.5 gallons which will cover 3 average rooms.  Doesn't sound to average to anyone with knowledge of this industry or a average house.  You are misleading consumers and should do a better job in your research.  No wonder so pay people think prices to get work done by professionals is high.  Its not high, its actually average which is more like $3700.

House Painter Co