LOTS of overtime. If he included his Per Diem and Profit Sharing that was paid in Jan/Feb, it is very possible.
Another thought, if your buddy was smart enough to bid a check airman line than he got paid for the trip he was taken off (FBO'd) and then picked up another trip and got paid add pay. We had some FO's making easily as much as captains by paying attention to the contract. These guys made out like bandits for not much overtime.