Justin Hall covers the Tokyo Game Show 2004 from the mobile perspective.
Flat-rate pricing for 3G is around $40/mo. these days but will have to come down more to really get wide usage. That said, it is a HUGE change in the industry and will ultimately be good for the customer.

Flat-rate services have arrived just in time; last year game developers at the Tokyo Game Show were complaining that high packet fees were stalling innovation. Now with the chance to take photos inside games and mail them around without running up big bills, future games might begin to incorporate mobile multimedia.

Playing with Mobile Media — Tokyo Game Show 2004