A lot of data has recently been shared about revenue numbers of popular iOS apps. Overcast [http://www.marco.org/2015/01/15/overcast-sales-numbers], Manual [http://williamwilkinson.com/post/108282752431], Dash for Mac [http://blog.kapeli.com/my-year-in-review-2014], Unread [http://blog.jaredsinclair.com/post/93118460565/a-candid-look-at-unreads-first-year] and Monument Valley [http: