I've only ever been to one stadium in Australia (and I've been to plenty) that does decent food for reasonable prices and that is Spotless Stadium at Homebush. Run by the RAS and set up primarily for the Easter Show.
It's been hell following the Wanderers there for the past 3 seasons at this shit hole and I can't wait to get back to Parra, but the food options are excellent.
There's a Subway, an Asian Noodle Bar that has a wide range of Asian stir fries, nibblies and noodle dishes, a Kebab outlet, a specialized Burger outlet, a seafood outlet and Pie Face. There's also a decent amount of designated coffee stands and temporarily set up BBQ's selling sausage and steak sandwiches.
If Spotless can do this, why can't other stadiums?
And, before anyone asks, no, they don't do fairy floss at football matches.