Amazon has been playing around with a pretty interesting business model lately, and their use of it involving Android apps has seen a 300% growth since its inception.

The idea is simple. Creators should get paid in proportion to the amount of time a consumer engages the creative content. Amazon first came up with the idea when crowds of writers with cartoonish dollar signs in their eyes flooded the Kindle self-publication platform with an unrelenting tide of werewolf erotica.

For years, Amazon had been trying to establish itself as a serious publishing operation, but eliminating the traditional gatekeepers of publication had some unexpected results. Suddenly, the professional writers they wanted to showcase had to dog paddle in a sea of poorly written lupine lust hocked at $2.99 a pop. Something had to be done.

Amazon solved their problem by introducing Kindle Unlimited, an intriguing system that pays a writer for how many pages a reader reads of their book. The werewolf erotica economy, which banked on titillated readers forking over cash in exchange for a few hastily read pages of drivel, suddenly collapsed. Now the people who began profiting were creators who produced well-crafted, engaging writing that found and maintained an audience.

As an encore, Amazon turned their attention to their Free App of the Day program, a system that provided a different paid app free of charge each day to Amazon device owners. They decided to replace Free App of the Day with Amazon Underground, a system very similar to Kindle Unlimited that pays developers based on the number of minutes users stay engaged with the app. Amazon Underground launched with a selection of paid Android apps (which Amazon device owners can access for free), and as of this week the size of that selection has tripled.

Hypothetically with this model in place, developers who create engaging and useful apps will be paid well by Amazon, and the developers who create whatever the app-equivalent of werewolf erotica is will get left out in the cold.

It’s such a new payment model that there’s no guarantee how well this will play out for developers. However, if you’ve got an Amazon device and the Amazon Underground store, it’s a win-win for you. More paid Android apps than ever are available to you for free. Might as well check ‘em out.