price is a personal preference. people i know charge in many different ways. i charge by 15 minute time gaps. it keeps me on time for my next client (which is very important) and allows them to decide whether or not they want to pay extra. i give them all a general time. all extra is made in advance and blocked out for their next appointment schedule.
it all is very personal. if it takes you 4 hours to paint marylin monroe, but your client loves it.........its different than someone who paints her in 20 minutes and their client leaves unhappy...(even if it was way cheaper)......its about quality, time, and being fair..... being honest and being real about the situation, the economy and so forth..........having happy clients who come back has no really dollar amount....some art i do takes 10 minutes and its the clients favorite design of their life...
just know:.........happy clients come back, they dont if you charge too much and prove them with little effort. they come back more if you provide extra effort even if they arent exactly thrilled with your end result...people love when you TRY to make them happy.
happy fun clients are hard to find. so, charging less and practicing and having a good time promotes happiness and having a gang of happy clients is wise because they come back and make YOUR JOB less of a job...unhappy ones pay more maybe..but they arent regulars and you cant wait for them to leave and every single moment it feels like your job is hell.
thats what i charge.