To be clear, most "top players" and really most enthusiasts will absolutely buy a console for just one game. Killer Instinct drove me to buy an Xbox One. Guilty Gear Xrd (if it ends up being exclusive, which I doubt) and Uncharted both have the power to get me to buy a PS4. Strictly as a value proposition, gaming consoles are incredibly attractive for the dollar points.
Sure, $400-$500 sounds like a lot, but considering the amount of time you get out of them in comparison to other entertainment purchases it's more than justified. I spend $20 on a brand new blu ray and nearly $30 if I miss release week. That'll get me about five hours of entertainment if the special features are generous. We'll stretch it to 20 hours over the life of the disc for re-watching the movie. Compare that to the thousands upon thousands of hours you get from a console even before buying games with all of the apps and additional services and it's pretty hard to argue against it.
This was a longer explanation than I wanted to give for the comments about exclusive fighters not being worth the purchase but there it is.