There's always the fable about the boss who declares that being even a few minutes late to work will cost employees the whole hour's pay, causing them to be reliably an hour late, all the time.

Works both ways. If you keep me in the office for a few extra minutes after quitting time I'm claiming an hour of overtime.

In the Cobra scenario, breeding a Cobra has no "cost" beyond the breeding of a Cobra.

If you reported a fraudulent bribe, which was reported to the police there is a risk the briber and you both are arrested.

It's however trivial to manufacture "real" bribes - hell someone could build an automated spambot spamming bribes to everyone as an act of charity.

That would fail the "credible" test for reward.

So now you expect everyone to engage with their bribers to determine credibility?

In addition, how do you even determine credibility when even real attackers might renege and not deliver on their promise of a bribe?