Andy_K 

This!

I can't even motivate myself to calculate the cost-benefit of biking to work, and I love data. I track my mileage. I track how much I spend on my bikes. I track the cost per mile for each bike. All of this is just to satisfy my inner nerd (who is even nerdier than my outer nerd). I don't make any attempt to find out whether or not I'm saving money because that's not why I'm riding.

Convenience is a factor for me. I'm lazy by nature. But convenience is mostly an emotional measure, so that gets rolled up into total happiness. I don't have a way to quantify this, but it's easy to regulate. Some days I don't feel like riding so I drive the whole way. If I drive too often I get unhappy about it so I figure out a way to ride the bike. If I have a reason to leave the house in a car, stopping somewhere and biking from there usually makes me happier than driving the whole way would. That is, the pleasure of riding the bike outweighs the convenience of just driving the whole way.

Let's be clear, riding a bike through the suburbs in a bike lane next to heavy traffic isn't something I would do for fun on my day off, but it's better than driving in that same traffic and I feel better physically when I ride.