While many analysts, environmentalists, and yes even economists will expound on the financial prudence associated with biking, no argument is better than actually seeing the dollars leave your wallet.
An example? Sure. How about, waking up, feeling kind of lazy, and deciding to drive the 3.5 km to work? And maybe, wanting to save a few bucks, it made sense to park in a plaza, only to return to a 55 dollar ticket affixed to my windshield.
That my friends, is an example of the 'real' costs of not biking.