They will make that argument, and the government will point out that Apple is trying to charge 27% everywhere those choice decisions were taken away, pretty conclusively proving... it's all about collecting the rent.
It's a no-win situation for them. If once they established themselves as the dominant player in the cell phone market they started undercutting everyone else on fees that could also be seen as predatory.
FWIW - this is further evidence of anticompetitive behavior. In a competitive market, entrants would be trying to drive distribution costs to 0. The fact that Apple makes its entire App Store revenue off those distribution revenues is highly telling.
It would only be considered predatory if they charging a rate below their own costs of distribution. I.E. If it costs Apple $0.10 to cover the costs of app distribution per download, then it would be completely legal for them to charge $0.11, but illegal and predatory to charge $0.09.
Which is not illegal.