If you get yourself allied with one of the factions at war, and take Massacre missions, then 30MCr is what I expect to make, mission payouts and combat bonds combined. (I've not yet tried Wing Missions here, but its possible a Wing of 4 could make more).
It needs to be said that you need to find a war with the correct parameters (I need large pads, and I don't want CZs 300,000Ls out, for example), and if your not allied that needs to be done, so there can be about 2 hours preparation, then you've got three days to milk it. But I quite like that there is some skill to maximizing profits from fighting other peoples wars.