[kepano]

Assuming you haven't exited to a barter economy you must surely be buying food? Unlike food, software can create time. Time = potential earnings. Consider a piece of software that costs less than a sandwich but the leverage it creates frees up some amount of time that earns you more than the cost of a sandwich.

[eviks]

Life isn't an ad, you can't monetize a random impression at any time.

Consider the software that saves you 5 min at night when you're doing some assignment - this isn't monetizable, you've go the benefit of 5 min more sleep, but you can't pay with that for the app

[kepano]

Converting time into money is easier for some people/professions than others. However converting less useful time into more useful time is a great thing for anyone. If an app gives you an extra 5 minutes every day, that's 30 hours per year that you can use towards something of your choice, whether it's sleep, exercise, recreation, work, etc.

Consider how much one hour of your time is worth — you are probably underestimating that number.