You forgot to include these services: character name changes, character race changes, character transfers, guild transfers, vanity pets and mounts. I'm not proud to say that I have spent money on all of these except the guild transfer service.
That is true, although as mentioned above the Chinese get their own deal. And Blizzard did get into the 'real gold for virtual goods market' which is quite large. Teasing apart the revenue per subscriber from their reports, talks, and sometimes off hand remarks is very challenging. There is the 'max' rate of $15/month, there are the 'free til level 20' players, there are the 'Yearly Pass' types, and of course there are the pay per hour guys in China and elsewhere in southeast Asia.
So my guesstimate at $10 per was a 'blended' rate. Pessimists seem to put it closer to $7, not sure why though.
