Maybe this article doesn't mean thing like ffxiv, but ffxiv did something similar. In essence if you bought it before it early released, you got to play it those 3 days early. If you wanted to play it that time you could have just bought it and if you didn't you just bought it 3 days later and played it anyway.
I think that for an online game that's a great idea, specially ffxiv, because the people that are going to play the new expansion probably bought it weeks prior to the early access and people who didn't probably haven't still finished the last expansion, so they really have no real incentive to play the new one like NOW, all they do is tax the servers for all the people that actually want to play the new content.
It's also a way to limit the user base into two peaks so that the servers don't die too much.
I'm completely against charging extra for the early access though. Early access maybe good, paying for it obviously bad.