Actually you are making a mistake: because a subscription is a subscription to WOW, be that cheap (like in South America or RUssia) or expensive (like western EU) compared to the US OR by having different systems in each country (like the PAY too PLAY cards in China).
Why is it a subscription ? Well you ALL play the same game and with the recently introduced mechanics in BOTH SC2 AND Diablo 3,
you actually already PLAY cross server these days in WOW ... too...
I mean ... I MEET Russians all the time in BG's ...
and they pay with a cheaper system already ...
The same applies for ... the Chinese that play ... on Korean sub models (and might I say with LOTS of Raiding successes)...
So for a PLAYER's position it is great to know we play cross server now and ALL play the game (just wait till trading and Guild play is integrated) and for the STOCK holders there is the financial REPORT and REVENUE.
So what's the problem ? Apparently we ALL play with apples, you just want to divide the colors ... when I play with different colors ... on my cross server ALREADY.