in atlanta, refill for a 10 lb tank is $9.
they dont sell co2 tanks though. i bought my 10 lb tank from ebay for about $85 brand new. but thats because i wanted a nice new shiny aluminum one.
i know some places do swaps and its alot cheaper. prices averages from $60-$90 from what i see members from around the net quote. but when trying to seach for myself, it was difficult trying to locate a place like that locally.