Want to play Star Wars: The Old Republic forever and ever? Each copy comes with a month of free game-time, but if you want to play after that, you'll need money: it's $14.99/£8.99/€12.99 per-month. That's exactly the same pricing structure as World of Warcraft.
Even the bulk costs are identical: a three month subscription comes to $13.99/month (paid as a one-time charge of $41.97/£25.17/€35.97), while a six month subscription costs $12.99 per month (paid as a one-time charge of $77.94/£46.14/€65.94).
So: here's a good game for your Saturday. You can afford to pay for one subscription game per month. What do you pay for?