Like Thomas said, the walk away pay isn't much. However, if you are good and unique you can make it. Look at Mark Rebilas, he's making a pretty good living.
I have a full-time job so it's not absolutely critical I make a killing. I will admit, I've done a few favors. Kind of the "I'll scratch your back, if you scratch mine". I've used those opportunities to build my portfolio.
But, to get back to the point, it's hard work. True it's fun to walk out into the stadium of a team that has won the last 2 national championships, but there's also the preparation, travel, working on a deadline, the pressure of the people looking at your work, etc...
If you want to do sports fulltime, expect to always be working; looking for new clients, working on current projects, etc.
It's very hard to gauge how much anyone really gets paid by wire services when making it to the next level.
It seems like you only hear hints when a picture does really well, like a stock photo of Johnny Football or a SI double-truck, but even for the Top 1% of shooters, that doesn't seem like a typical payout.
Have you averaged the commission received from every event you covered last year?
As a rough estimate, a major event would be at least an 8-hour day... travel, parking, pre-game, game, half-time rush for a couple of quick submits, 2nd half, quick post-game rush for a couple more quick submits, travel, edit, tag, upload.
If you managed to cover 52 major events in a year, would you clear an average of say $1000 per event?
Or is it more like $200, so a HS kid who dreams of skipping college and being a "pro sports photographer" would have to find 250 events (5 days x 50 weeks = 250 working days), to have a chance at being able to make it a full-time job?
FWIW, for my spec youth and varsity coverage, I track the commission for every event. It's a bell curve, at the low end it's sometimes only $10-20, a few times a year I'll clear $500+ at an event. But my average has increased from $60 to $90 per event. Each event averaging 4 hours when including post-processing. So $15-$22.50 per hour. After taxes, insurance, and equipment, I could probably make more in the concession stand.
I know take home pay is always sensitive, but since you offered "ask away" I figured this might be a good candid thread to ask in.... Does the average photographer at a NFL game make more than the average beer vendor at an NFL game?