You know what I think would be neat? Subscription fee being roleplayed in game as "Taxes." If you aren't online at the time your subscription is due, you'd get a letter saying your city taxes were received, and thanking you. If you were, a tax NPC would show up. Hee hee...
It won't happen, I'm sure, but darn it could be funny.
Or, maybe you have to go to a town hall to "pay" your taxes. Kind of like how you "Pay online?" I don't know... would be a nice little added twist in a game.
As for paying for items with real money... meh, I don't believe in that. The point of online RPGs in my eyes is even if you can ONLY afford the subscription fee, you can still be someone amazing with grand items. If they did that, only the rich would look neat... the poor would not. That's the kind of reality I'd rather escape.