[M]ost of the things we buy have to be paid for twice. There’s the first price, usually paid in dollars, just to gain possession of the desired thing, whatever it is: a book, a budgeting app, a unicycle, a bundle of kale. But then, in order to make use of the thing, you must also pay a second price. This is the effort and initiative required to gain its benefits, and it can be much higher than the first price.