The ranking mentioned is also the "Top Paid" one. That is pretty meaningless for a relatively inexpensive app ($2) in a niche category.
My direct experience has been with the iOS App Store where I've never once been above #25 in the top paid photography category but am always within the top 10 of top grossing photography. I make considerably more than $15.42 in a day because I charge more.
2. This was only over 1 (ONE) day.
3. This was in the Dev Tools category.