From their F.A.Q:
We have not made final decisions about the cost to play. There will be a retail fee for the original purchase, most likely in line with standard PC titles. In addition, it is likely that we will go with the industry standard of paying per month (or 3, 6, 12 months) of play. We are investigating alternate payment plans, and should any of those be feasible we will offer it in addition to this standard.
Payment options for a monthly subscription fee have also not been finalized. It is likely that we will provide multiple options, and that a credit card will not be the only method of payment. We realize that not everyone wishes to pay in this manner, and will be working out details for these users as well.I generally hate MMORPGs that charge you money each month eventhough physically it's impossible to play the time you are actually paying for. It's insane...
Still... perhaps if they go with ads in this game they could let player pay only for the one-time fee.
All that aside, I'm pretty interested in this game,
Cheers