Hi Jeremy,
This is difficult to answer, because it will depend on a number of things and your geography. I use a local "pro-lab" for color stuff I care about (non-snapshot photography). I rely on their quality film processing and pay a premium for their good dependable service.
Cost to cross-process will also depend on what you have them do. Push/pulling is extra at some places. Do you need a contact sheet, or just proof prints? All that is extra.
It's been a while since I've done 35mm film cross-processing, but I think I paid about $20 for a 36 exp. roll, with a 8x12 contact sheet about a year ago. YMMV.
My advice is to find a good lab who does consistant work for you. If you tell us what part of the country you live in, someone might be able to suggest such a lab.
Good luck! 🙂
rt
ps. I had some luck x-processing fuji tungsten chrome 64T (slide) film. Have fun!