GREED?! Utter nonsense! The FO was on $16,000 a year, the Captain around $40,000.
For risk of a thread drift if they couldn't afford what the position(s) entailed, perhaps 8 hours horizontal rest pre-flight and all that, then they should never have taken on the position(s).
Did they explain to the passengers, that they killed, before departure "Excuse us but we are too tired to safely operate this flight but you are welcome to take your chances with us should you choose to do so"?