I got the Galaxy S I a few months ago (didn't want to pay more for the II, even though it looks like a much nicer phone). 55,000 a month, +9,000 / month for the phone, + taxes = 73,000 / month for me. Note that he 'unlimited usage' is only for data. You only get 300 mins / month for voice calls and 200 texts (I think). Of course, there are 'solutions', like Skype and Kakao Talk.
There numbers for for the Galaxy S I...don't know about the II.