The pro badge is no more, and pro accounts exist only as grandfathered in plans. You can renew an existing pro account, but those who aren't currently can't subscribe to it.
As I understand it, accounts that were originally a gift, like mine, don't get the recurring transaction treatment. This makes sense, but only up to a point, that point being where the owner of the account renews it with a different credit card and it becomes truly "theirs".
I am not sure that flickr gave this scenario due consideration, there must be a lot of people who received pro as a gift but have since paid to renew it will be unable to benefit from the reduced "grandfathered" price of $25.