The article is from 

February 19th, 2008 by Geoff
For as long as I can remember MMORPGs have had a monthly payment plan, decent ones at least. Back in the days when I used to play Ultima Online and Nexus these were new ideas and ones that were strictly taboo amongst mainstream society. Hell, you couldn't even really play normal video games back then without getting odd looks from most people. So, suffice it to say, paying a monthly bill to play one was virtually (haha I'm punny) unheard of. Of course, these games were both about ?10 a month, a simple fee that I didn't think much of at the time. So how did ?14.99 become the standard for mainstream MMOs today?
Well, there isn't exactly a history of MMO subscription fees lying around the intertubes. If there was it would make answering this whole question a hellofalot easier. So, what I am putting forward next is very clearly my own theories and conjectures. That said, I do believe the 14.99 price fee began with the inception of Everquest by Sony Online Entertainment.
Everquest is touted as being the first fully 3d MMORPG (I'm not sure if it actually was or wasn't). Because the game was one of the first it was justified as being more "costly" to produce. Now, the cost to produce and develop a game is largely dependent on the technology of the time. We probably will never know exactly how much it cost Sony to make the game, but given the technology available it could have been less expensive to develop the title than even Ultima Online. However, due to it being introduced as cutting edge technology Sony was able to use that as a fall-back in order to secure the right to charge more than it's 2d brothers of the time being. When the game launched in 1999 you had to pay a US 14.99 monthly charge.
So how did this affect the rest of mainstream MMO society? Well there is a very simple answer for that, Everquest was successful. Because the the popularity of the title it gave Sony, and other developers such as Turbine and Blizzard, validation that US 14.99 was a good fee to use to charge gamers monthly. Had Everquest failed we'd probably see games still hovering around the US 10 monthly mark. Now, this goes without saying, that as more and more MMOs come out the US 14.99 charge could be more. Especially when a certain assumed mega-blockbuster title is hinting at that very possibility. Who knows? Anything is possible. . . I'm just theorizing here.
[Editor:Stella]