To be more accurate: higher dmg and more hits does not equal more income.
The clue is %dmg done to the ship.
For instance - killing dd in 2 salvos and dealing him like 10k dmg will give you more money than dealing 40k dmg to bb with 30+hits.
So basically if you want to earn good money in Atago, try to hunt for DDs and use APs against cruisers.