In this world of ours nothing is for free without a cost of something. So when it comes to good decent MMO's you must pay for them. But would you rather pay monthly or yearly for a subscription for a MMO?
There is usually a free trial when you buy a decent MMO game or one made by a big company if I see myself playing the game for a year or more I pay for a yearly subscription. Plus, I think if you pay yearly, you might get a discount.
Some banks charge a $1 electronic fund transfer fee, so you be out $12 instead of $1 dollar if you keep taking money out of your bank account to pay for a MMO every month instead of once a year.