1. The consumer purphases product A (here the coffee maker) on the normal consumer market we're all familiar with.
2. Doing so forces the consumer to purchase product B (here K-cups) on a different market.
Keurig's goal is to control the second market. By making having all the market power, they can jack up prices to the consumer's detriment.
The reason you see companies like this invoking the DMCA or using DRM is because they have no actual competitive advantage in that second market. They are at a disadvantage because they burned money selling product A at a loss to get people into their market.