the issue is getting a hard enough coating on the rim that will with stand some abuse. paint isn’t really the right product. It will chip and the old finish will show through, if they have been anodized then paint will not key tp the surface well. Any flex (and wheels need to flex) would crack the paint.
So powder coat is the best option for a refinish, prices will vary, Coats tend to do big batchs of one colour, so if you like the colour he is doing that day just getting the rims done might be dirt cheap (beer money) but if you want ocean otter purple then its going to cost and take time.
you’ll need to factor in the costs of wheel builds, the eyelets in the rims will also get coated aswell.