My guess: being on one of the top lists in an app store is a ton of exposure. One of the biggest problems with selling apps is getting people to know it exists.

My guess: being on one of the top lists in an app store is a ton of exposure. One of the biggest problems with selling apps is getting people to know it exists. Once it fell off the top paid apps list, it suddenly got far, far harder for people to find it, thus the dramatic drop in sales.