Making over 600k credits in one game?!

Lert:   It was already said those were missions ... As for expert - I'm just a slightly above average player with a long memory and a workable understanding of game mechanics.   Those missions were ran a while back. WG would have missions where if you did 25k damage total in a 24 hour period you would get 350k credits, and similar ones. Those were golden days. Unfortunately, they don't run those amazing credit missions anymore, so you're kinda out of luck.