What maintains one vice would bring up two children.

Habits have a running cost, and that cost is usually invisible because it arrives in small pieces spread across a year. Added up, the sum is often startling: enough to have paid for something you said you could not afford. That comparison is the useful part, more than any judgement about the habit itself. Money leaks at a rate you would never approve if asked for it all at once.

Take whatever your most regular small expense is and multiply it out to a year. Then name one thing that figure would have bought. Keep the habit if you still want it, but now you know its price.