[Tom Edgerton]

Daniel Greene once remarked that he adds 50% for complex backgrounds, defined as anything that's more than a compatible neutral plain background. Most of the artists I know add around 25-30% for such.

It's not just to underwrite the additional effort in doing a complicated scene--I've also found it helps to keep clients who are proud of all their stuff from loading down a portrait with too much extraneous material crap. (They'll be less inclined to ask you to paint the Beemer outside the window if they know it's going to cost more.)

It gets pretty funny sometimes. We were once given a formula at a national conference that dogs and cats were an additional $500 each, and a horse is half a person.

The quick formula given out at the same conference was to charge around $1000 less for pastels than oils, if you did both. So an artist whose average price for an oil might be $6000 would charge a grand less for a pastel, all other factors being equal. So as you can see, you wouldn't discount a pastel by half, for sure. (If you don't charge on this level, maybe the above info would be a guide for working out an equivalent percentage for pastels vs. oils.)

Hope this is helpful.