The difference between subs and accounts are huge considering the fact that you have to pay for a subscription. If WoW was free to play most, probably all, of those who have stopped playing would still have an account since it doesn't cost them anything to keep it.
That's why it means nothing to say that you have X number of accounts since you have no way of knowing how many of those are active. When it comes to subs it's a different thing since you have to pay to have an active subscription, something you won't do if you don't plan on playing.
- - - Updated - - -
But they also have $3 billion in cash on hand right now.
"The transactions announced today will allow us to take advantage of attractive financing markets while still retaining more than $3 billion cash on hand to preserve financial stability."