An interesting idea from this Slate article on the relationship between health and wealth:
The “health-wealth gradient” refers to the fact that, as a general rule, the richer you are, the healthier you are. This applies across different countries and across the full range of social classes within the same country. (It’s not just that the very poorest people are sick.) No one knows exactly what causes the health-wealth gradient or why it’s so resilient. It may be that rich people have access to better health care. Or, as we’ve seen, it could be that being sick costs you money. Then there’s the possibility that poor people have a greater incentive to behave in unhealthy ways: Since they don’t have as much money to spend on happiness, they “spend” their health instead. (The pleasures of smoking and eating, for example, are easy on the wallet and hard on the body.)
Specifically it’s that last sentence: I had never thought of health as something you spend, but of course it is. I, for one, know that I go to the gym at least in part so that I can eat whatever I want. I am essentially purchasing health credits at the gym which I then spend on less healthy activities that I enjoy. Wow.