The idea that someone could make a rational decision is almost strange. The idea that the decisions might not be rational could be even stranger.
The point probably is that whatever the decision is, it always follows some kind of rationale. However, what it probably never is, is a rationale the individuals are entirely aware of. And what it also rarely is, is a rationale shared by all those curious about the decision.
When people point to a decision and discuss how it isn’t rational, what they want to say is that they cannot make sense of the decision.
What can also be said is that in such a decision process, there will be some aspects that may have been pushed out of awareness leaving space for the hope of being right or having made the right decisions in the past. But it doesn’t mean that cost or other measurable items must be in the center of one’s decision.
Keeping an eye on what is right for oneself, however, needs to remain central.