Invested too much in my car! How can it be worth cycling to work?
It is a known psychological fallacy (sunk costs fallacy) that already having spent too much resources (time, money…) on something that turned out to be a mistake somehow justifies persisting in doing that instead of switching to something else. Because it is irrational, it is hard to use rational logic to persuade.

Maybe pointing out that the very feeling is irrational, and that feelings should not be placed before logic and hard data when making certain decisions will help somewhat. Point out that new information obtained later on can and should affect people's reconsidering of past decisions, instead of living in the past. Also, maybe asking on a forum dedicated to psychology will give better results.