I'm always eager to upvote a Game of Thrones quote, but unfortunately I don't see the rationality insight here beyond an ordinary quid pro quo.
Tyrion is frequently put into situations where he relies on his family's reputation for paying debts.
It's a real-life Newcomb-like problem - specifically a case of Parfit's Hitchhiker - illustrating the practical benefits of being seen as the sort of agent who keeps promises. It's not an ordinary quid-pro-quo because there is, in fact, no incentive for Tyrion to keep his end of the bargain once he gets what he wants other than to be seen as the sort of person who keeps his bargain.
Think it's a stretch?
Another month has passed and here is a new rationality quotes thread. The usual rules are: