San Francisco-based developer Giacomo Balli doubled his take on his iPhone apps thanks to an April Fools’ Day joke. When he ratcheted up the price to an eye-popping $4.99 for an app that catalogs books, he got downloads instead of complaints.

The App Store lets devs change the sale price of their apps pretty much any time they like, but most folks take conventional routes: cutting prices during sales or dropping prices to free. Balli made his previously free apps premium with just a toggle.

“There weren’t any app updates, either,” he told Cult of Mac over the phone. “Just the price.”

FastTrack Navigator is just about the simplest navigation app you could ever want: It’s a big arrow on the screen telling you the direction of your destination, along with a number telling you how far away it is. But that’s not to say that it isn’t beautifully designed.