Do I have to invest anything to be a fan of a sports team besides time? No. Do I have to invest something to enjoy the product of say Nintendo? Yes.
Unless you listen to your games on an old-timey radio, I'm sure you purchased a TV to watch your sports team, and possibly paid cable to watch it if you are out of the region. And if you're in the region, and wish to see a particular sports team, I'm sure they would require some kind of fee at the gate of their stadium.
Of course, you could just watch games in a bar, that's free, I suppose. Or just happen to walk by a TV store with a game on.
As a counterexample, you don't have to financially invest in video games to enjoy them. There are plenty of free flash games and facebook games and dollar apps out there. Some even have pretty big followings, like Angry Birds.
Nintendo fans can be a special breed when it comes to the company itself. Their financial successes this generation spat in the face of those that openly bet against them and wistfully opined, almost wished, that they get out of the hardware business and make iPhone games. And the defensiveness of some of Nintendo's more extreme boosters comes directly from that constant assault, sometimes in the face of plain facts. In an ironic twist, it is this assault that creates the "sports team" effect, because it makes the fans defensive, making even some of the more curt critics in Nintendo's fandom circle the wagons along with the zealots. IT's sort of like a brother that you make fun of, but when somebody else makes fun of him, you stand to protect him.
While the sports team hare with the fans the goal of "win," Nintendo fans have a similar goal they share with Nintendo. "Survive." Right now Playstation fans are probably having this very wish right now, even if they didn't financially invest in them with a Vita or a PS3. Sony's bleeding out money such that even if all the fans bought every Vita game 10 times, it may not be enough to save their gaming business or at least some of their better studios. But I bet they would want them to survive due to memories of their first Playstation games as children. They may not want that part of their childhood thrown to the wolves, even if the company made stupid decisions.
Well that was rambly, I guess my point is that you can be a booster of something even if you have to financially invest in it. Heck I think that might even be one of the definitions of "booster." Sports fans are not better fans than video game company fans just because they can find ways to enjoy their sports teams for free.
I play video games before companies.
But I find that the people who get most up in arms about fanboys are generally assholes, so no one's as squeaky clean as they think they are.
Oh god don't I know it. The guy who comes in and rags on "fanboys" and fancies himself as "objective" is probably the most disingenuous and stock forum character that ever was.