If you're going to sell out your allies, make sure to do it for a huge amount of money. Paid in advance.

Transcript

Luke: So Han was feeding Vader information all along?
Han: How do you think we managed to escape from the Peace Moon?
Han: Chewie and I ran straight into a platoon of clone troopers and got captured.
Han: We agreed to lead the Empire to the Rebel base, in exchange for a huge payout.
{flashback to Han and Chewbacca fleeing the Peace Moon}
Han: I'd call that a successful negotiation.
Chewbacca: In that we are still alive, despite all indications to the contrary?
[SFX]: Pow!
Han: Nah, instant profit!
Chewbacca: It is not precisely what I would consider cash in hand.
{back to present}
Luke: Chewie was in on this too??
R2-D2: Et tu, Ben?
Chewbacca: To be fair, one doesn't often get the golden opportunity to be a treacherous lying bastard with a silver tongue.
R2-D2: Oh geez, I come here to get away from my day job!