Tampa Bay really #12th

I have to say I was more than surprised when I saw this story this morning Forbes says Bucs are 12th most valuable team, in the world | ProFootballTalk.com. I mean the Cowboys, Yankees, Redskins and Patriots all make sense but for Tampa Bay to be in the top 20 I'd have to say I'm certainly surprised and some what skeptical on what criteria they use to figure out this list.