http://www.screencast.com/users/GroveCanada/folders/Jing/media/9e26779c-f609-414d-adb1-d0a0a6fadd1f (THIS IS A SCREENCAST EXPLANATION)

So...

Your costs are $200.00 (say paint plus canvas etc.)

Your labour is 1000 minutes...(like 16 and a half hours...)

At $18 dollars an hour that comes to $300.00

Your overhead is $100.00 (rent, lunch, computer etc.)

So...Your wholesale price is (costs of supplies plus+ labour+ overhead) times X 2 = (200+300+100)x2= $1,200.00

Your retail or keystone pricing as it is called is the wholesale price times either 2.5 or 3...

So, your retail price is: $1,200.00 X 2.5 = $3,000.00

Thanks to...

Pricing Variables and Final Advice

p.s. of course, from there you can put stuff on sale knowing your margins...