Money: What It Costs

Arabs in dusty white robes queued up outside a government bank from sunup to sundown in Cairo last week.

In the back streets of Hong Kong, men ducked through the beaded curtains of dingy little stalls, later reappeared clutching envelopes. And in Rome, workers with small salaries and large families stood hopefully before the cashier windows of pawnshops, known popularly as the monte di pietà — mount of pity. All of them had one quest in common — money — and they were willing to pay a price to get it.

Just how much money should cost —the interest paid on...