Yes the pricing does change, and quite significantly. I have worked inside the paint industry on counter sales outside sales and application for over 10 years. One thing many people do not understand is, the resins in the paint are more expensive to produce the higher the sheen goes. Therefore the company is at of higher cost making the paint, which in terms they charge more for the paint. I have seen a 15$ variance between flat-semi-gloss it is not uncommon and is not unrealistic to pay more for a higher sheen. Another thing to add is when doing samples on your wall prior to a painter coming is a good idea, however do not do them in huge squares with heavy coats, remember you are just wanting an idea. A lot of times the issue comes up of the paint not covering the sample coats, in fact it is covering quite well, however the paint sample applied is often times much darker than the wall color, creating a contrasting difference from the lighter surrounding wall and the sample placed on the wall. I recommend getting a piece of sheet rock and using it for the samples so you can move around with it etc.
When selecting a color scheme for the home’s exterior homeowners can choose color options that will correct flaws that they may feel exist with their home and property.  Some examples include utilizing two shades of a single color to make a home appear appropriately sized when the home may be too large or too tall.  To accomplish this effect individuals will want to place the darker tone on the upper level of the home’s exterior.  Smaller windows can appear more proportionately sized by trimming them in a lighter tone of paint.  Darker colors make a space or feature appear smaller.  The same effect can be obtained for homes positioned further away from a curb.  By using lighter tones the home will not feel camouflaged.
Watering down the paint 50%? It will not cover. I am a contract painter and found that most people that I make a contract with immediately try to change the deal and get more than they are paying for. Sometimes, I let them cheat me as they may have other work that I wish to do but other times I put my foot down. I try to get the client to look at what I have done each and everyday if I am going from room to room. I cannot do this If I spray the entire project at once. Even when I have them inspect my work, they often just do not tell the truth and wish to scam me the contractor for more and more while paying the same as the original contract. Most people have not a clue how much work is involved in painting a house and just assume that the painter rolls out the work with no prep, sealing off the place to protect things that are not painted. All of my contracts state that if anything is in the way like babies, dogs, cars, plants and furniture that I cannot proceed and that it is their responsibility to move this stuff. I always seem to be turned into a furniture mover and never get paid to wrench my back. Fact is most people try to rob the contractor and this article tries to make it seem that the contractor is robbing the homeowners. My sister is a prime example of this as she always goes for the lowest bid yet expects a world class job. This means if you pay $500 for a two day paint job do not expect the contractor to live at your home for two weeks and make only $500.
A painter's rod, or pole, can help you paint ceilings more quickly — no climbing up and down ladders required. And there's no need to stand directly underneath the area you are painting, so you won't catch every wayward splatter. A pole is also great for walls and floors. The pros were split over whether the 4- or 8-foot pole is best for everyday use, but they all agreed that a telescoping rod is the best bet.
To win work, contractors generally have to bid against other suppliers. To make an accurate bid, they estimate the time and materials required to complete the job. They measure the area to be painted and discuss the type of finish the customer requires. They assess the quality of the surfaces to work out how much remedial work they must carry out before painting. They might have to remove old paint or wall coverings, or repair cracks and other damage. They also calculate the cost of any essential equipment, such as scaffolding for exterior walls.

House Painter