if you ship them out the way that fu98 is saying i have had first hand experiences with a friend who tried shipping them out via ups and fedex, and i guess sometimes you gotta find the right place to ship them out because sometimes they will not let you ship it out that way unless you are a major wheel company who does this regularly, such as tirerack. so before you go wrapping it up in tape and cardboarding the faces, make sure the company you want to ship it out with will let you do so.
i have shipped out pretty much every set of wheels i have sold, and i have found that the best place to get boxes to ship them out in are the trash cans behind the wheel places, such as america's tire co and just tires, because they regularly throw away boxes from their wheels. if you want, you can even ask them if they have any that they will be willing to give you. at this rate, you will be able to save $$$ instead of buying boxes. other than shipping, all i had to buy was a couple rolls of tape, which can be had pretty much anywhere.
I have used a box for a 20" wheel to ship out 19" wheels+tires, and found a 22" wheel box and cut parts of it to make it fit around a 20" wheel+tire. i then used another box to put around the faces of the wheel, and folded up pieces of cardboard to fill up the corner gaps between the tire and the outside box. as a result, you will be using 2 boxes for each wheel you ship out. after that, just wrap it up in a lot of tape. the more tape you use, the more peace of mind you will have that it wont open, and thats also more cushion too!
realistically, imo, shipping will cost under $200, i have yet to encounter shipping a set for more than $180. IMO local buyers would be a lot easier! haha, shipping wheels is a PITA!!! good luck guys and gals!
Falken Tires | Function & Form Suspension | Meguiars