Powedercoating is actually pretty cheap. I work for Bast Tire and Auto service as a commercial Tire technician, and we have a Powder coat shop in the building. I deal with alot of customers who want their rims refinished in powdercoat, Our prices are about equivalent to $45 US to have a wheel bead blasted, apoxy primer'd, top coated (powder), and powder clear coated. A good powder coat is probably one of the best types of paint, its just a myriad of possitively charged paint particles sprayed onto a negatively charged part, then cured in an oven at 400 degrees for x amount of minutes, the paint particles melt and form a very durable and consistent coating on the part. (for those who are interested but dont know how it works) A good powdercoat finish will be equivalent to the finish found on most house-hold appliances such as Stoves/washers and dryers...even on alot of ATM bank machines. It also comes in several colours/textures.

Edit: The only thing to watch for if your going to have alloy rims powdercoated is the blasting. Alot of commercial powdercoating shops use heavy bead blast that will actually cause the finish to be rough(it was mainly designed for 8x22.5/8x24.5 mild steel rims off transport trucks) So make sure the rim is blasted in a fine bead shot, or perhaps sand.