You can now pay for blocks of 1,3 and 6 months. The cost is more then a subscription for various reasons. You do not need a paypal account to buy the blocks so its a good way to get premium before your paypal account is set up, and its an option for those who can't get a premium account.
If you can get a subscription, thats the preferable way to go. With paypal subscriptions we can hand off a lot of the work to them. With the blocks there is more personal intervention required to make sure payments were sucessful and valid. The extra cost is to make up for the extra checking we have to do to put this system in place.