This is the "You don't need to pay the whole price, pay only what you use" scam. Based on the fact that people don't know how much they need and when they need it. Like electricity being cheaper at night or at certain hours but being mainly used during the day (those people cannot afford electric cars, they have to wash during the day with a noisy washing machine and they have to cook during the day).
You would not believe how much more money they began to make once they started selling power using scratch cards. It was n-times the difference.
People, paradoxically, spend more when they can easily see how much they spend.