I never optimized for revenue. Given the high retention rate and overall user numbers I could have gotten way more out of it, but I was frankly not interested in it. I felt like I was making good enough money given the effort that I put into it. I used standard AdMob, without any mediation and replied with "No, thank you" at least twice per week to random people asking me to buy an ad slot in the app.

The numbers fluctuated quite a bit in the beginning but were relatively stable during the last couple of months. From AdMob I'd get between 25€ and 30€ per day and IAP made up for an additional 15€ to 20€ per day.

Obviously before taxes, but given that my running costs for the app were exactly 0 and I sometimes put equally many support hours into the app, I was more than happy with it.

EDIT: Just to clarify, those are pretty much peak numbers. I didn't add revenue stats to the article because I'd have to properly crunch the numbers them first. If you just multiply those by 365 you end up with way more than I generated over the entire 2 1/2 years.

same. very interesting article, and interesting to hear about the distribution between income from adds and people paying to remove adds. But I for one would be also interested to get a rough estimation of what finding a nice little niche space like this could bring you in terms of revenue

7k downloads per day... At one point 1/3 of revenue from the in-app purchase to remove ads.