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.
I am in northern Nevada and you have not yet gotten sufficient responses to provide a painting cost chart showing the averages. I do have a quote from an outside (Not Homeadvisor referral) painter who is local for $2,750 for soffits, patio cover and posts, Garage facia (redwood clapboard above (~300 ? Sq. Ft.) on a 2046 Sq. Ft. home where the walls are 9 ft tall and it is fully stuccoed with plastic stucco surfaces, so not being painted.