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.
In general, glossier paints are more stain-resistant and scrubbable. But a higher sheen also highlights any imperfections in the wall or in the paint job. "Flat paints are fine for ceilings and formal rooms, but for most of my customers, I recommend an eggshell gloss. It's good for hallways, kids' rooms, even kitchens and baths," says Toto. It seems that latex paints have won over even the most finicky painters. "Though we still use oil-based paints for restor-ation work, latex paints are fine for interior walls and new trim," says Toto, "as long as you don't go cheap on the paint." All of our pros have their personal favorites, but they agree that good paint does not come cheap. "You'll spend $20 to $35 per gallon for a top-shelf paint," says Weeks. The pros also agreed that using two coats of paint will result in the best-looking job. Don't skimp on the coverage; if you're covering more than 400 square feet per gallon, you're spreading it too thin. Also, keep 1/4 to 1/2 gallon on hand for touch-ups.
Historically, the painter was responsible for the mixing of the paint; keeping a ready supply of pigments, oils, thinners and driers. The painter would use his experience to determine a suitable mixture depending on the nature of the job. In modern times, the painter is primarily responsible for preparation of the surface to be painted, such as patching holes in drywall, using masking tape and other protection on surfaces not to be painted, applying the paint and then cleaning up.[2]
His team is very meticulous, very careful, very clean, and very courteous! They're also very accommodating. For instance, I mentioned a couple spots under some angled siding where I thought a little extra filling was needed, and they obliged without question. Same thing with a request for a stain-proof primer under a balcony. Doing these kinds of little things without question or extra charges is really nice! 

Paint Contractor