Lap marks are those ugly stripes caused by uneven layers of paint buildup. They occur when you roll over paint that’s already partly dry. (In warm, dry conditions, latex paint can begin to stiffen in less than a minute!) The key to avoiding lap marks when doing DIY wall painting is to maintain a “wet edge,” so each stroke of your roller overlaps the previous stroke before the paint can begin to dry.
Some contractors work on time and material others on a firm contract. I would never hire the former and am leary of the latter. A contractor may low-ball a bid to get the job planning to make a killing on change orders. If you say good morning to them, they charge you extra for that. If the contract is not very, very specific and extensively fleshed out or if they display their change order schedule prominently on top, show them the door.
Not only careful communication is essential, but we would greatly recommend, when you pick out your type and brand of paint that you go and pay for it, with the contractor's discount, which is given by Sherwin-Williams and most paint companies. Then you will know how much paint you purchased and the coverage. If it is possible, inspect the work of the painter daily.
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.