When the service was first announced, a premium price was going to be attached to the service, but since launching, Real ID grouping is not part of the premium package -- it's free for everyone. Blizzard reserved the right to add features to the premium suite of WoW services, but this one is here to stay for free.
I was skeptical about the costs associated with the service in the beginning, but after trying out the service with fellow WoW Insider editors, I was hooked. Paying for the service, however, was not something I would have done. Players have a certain expectation about what they get with their monthly subscriptions, and in a world where free-to-play MMOs and games charge small amounts all over the place for items and boosts, a subscription game in the vein of World of Warcraft has a harder time justifying the extra costs because of the nature of the monthly subscription beast. It is nice to see that Blizzard is adding this feature for all players, no cost attached. Hit the jump for the full announcement and FAQ.