But you miss the point that media revenue isn't the only thing that matters.
The AFL might get 30k TV viewers in Brisbane, to Brisbane Lions games. But say they got 100k instead. What benefit is that to the AFL? They might be able to sell media rights for a few million more a year.
But Brisbane Lions get 300,000 attendees to their home games a year. 10 years ago, when they were bad, they were only getting 200,000 a year. The benefit of that 100,000, via memberships and ticket purchases (and more minor things like merchandising) is worth a lot. If we use a rule of thumb that they benefit $30 from each additional attendee, that's another $3 million.
What does the AFL spend this additional 3 million on? Subsidising Auskick in Queensland. It is cheaper to do Auskick if you live in Brisbane or Gold Coast than mod league. Which is why AFL don't just care about how many people in Brisbane watch a Brisbane Lions game on TV, they care about participation numbers.
Now, the AFL are not doing this out of their goodness of their heart because they love the idea of little Johnnie running around kicking a sherrin over a steeden. They would hope that, in 20 years' time, as little Johnnie becomes big Johnnie and he moves to Sydney to become a bigwig at a bank and is too busy to care about sport, NRL or AFL otherwise, he holds a more positive view of the AFL having played it as a tacker, and therefore will convince his bank to sponsor the AFL instead of the NRL.
There's more to the AFL and NRL strategies than discussed here. It's complex.