What's the cheapest way to ship luggage to the United States?

Looking for a little advice about shipping things back to the United States. I was planning on sending my large suitcase back to the States and then continue puttering around Asia with my carryon. Does anyone have any tips, experience or methods for shipping something (about 70lbs) as cheaply as possible back to the U.S.? It does not have to arrive with any real speed - it just has to get back eventually.

Thanks!