Can you update subscription option?

[Xieveral]

No MMO I know of has an hourly rate, probably for the same reasons.

That is how games in internet cafes work. The thing is most of these games aren't run by the parent company themselves but by another company that paid licensing fees.

You can't just throw down a quarter and claim a computer for half the day. What you can do is buy a timecard in advance and only be charged for the time played. The timecard is usually much more than one would pay for a subscription, though.