Bumidan! You've found an area with a lot of interest, I expect you'll recieve the interest your threads have always deserved here friend.
Now regarding cost: Development is going to be a big one!
Each chair costs Sony ~100k per year. If you look at EAs recent layoffs of ~500 people to save ~50 million dollars then it holds true.
A very quick and easy analysis for payroll costs is simply total the quantity of developers and multiply by $100,000.
Regarding operating expenses -> PSN would probably cost more than Xbox Live to manage and run as they rely on servers rather than P2P like a lot of Xbox Live games. There are two other comparable services currently, Steam and Xbox Live. Steam most likely relies on a margin on each game to run its servers so effectively brick and mortar store margins = server upkeep for them. I have no idea how to work out the cost.
Another thing with PSN is the frequent updates to the service, remember there are programming and testing expenses with the frequency of updates they have. Remember 100k per year per person.
Since they have so many projects coming to fruition next year you would expect to see personel costs rise reasonably quickly as headcounts tend to increase nearer to release.
For example, Guerilla games has 130 employees so it costs them roughly $13,000,000 a year to feed those numbers, if the game has taken say 3 fulltime years it would cost them $39,000,000 aprox to develop excluding contractors and third party companies/technology.