none ... it's a international company and the difference is due to open market competition. last time I checked, I had 19 options for prepaid SIM cards, which keeps the market quite competitively priced. i'm still shocked that some people tout what T-mobile offers as a prepaid SIM (technically it may be true, but holy crap are the terms awful.) i just picked up a dual SIM phone (Nokia 206) though and i'll pick up a prepaid t-mobile SIM next time I'm in the states just to have a US number for my idiotic friends that can't handle a +49 or 0049 prefix :(