When I start to think what to write I noticed that it may not be short, so for the impatient I say I earn $50 daily through banner ads nowadays.
If we dive into details; I am a game programmer and I use only banner ads for now since google still doesn't support selling apps in my country(Turkey).
At first I released a simple game to see how things work and it didn't work so well :). The game was something like billiards but has a unique game play and a unique name so it did not well on searching. Then I tried an air hockey game since I thought it is something that people would search for. It didn't work either. They were making less then $1 daily.
These were global attempts but then I notice some gaps in local market. There were some popular card games in Turkey. I developed the first online versions of these games in android. They become popular by the help of being the first and become addictive by the help of the chat feature in the game :p. People spend hours in the game. They play even while driving(and chat at the same time, I don't understand how they do it :s). So the ad impressions reached up to really high numbers compared to the number of downloads, there are some who spend 9-10 hours in a day :|
Last year these times with the first one of these card games I started to earn somethings notable, around $30 daily. There were two other games I was going to develop. I was thinking I could have a decent income when I finish them. I published the other two games. Users increased but the revenue did not, then I learned that the companies try to spend the advertisement budgets around Christmas, remaining of the year is not that profitable in terms of ad income.
In spring I was busy with development-bug fixing and trying different ad networks.. On summer I filled the apps with different kind of ads,(banner, notification, shortcut icons..) and at most I could get $90 daily.
At the end of the summer I started to work in somewhere so I was able to relinquish some part of the income and I removed some ad types which I found annoying. I left only banner ads in the games. The revenue from banner ads also started to decrease and daily income dropped less than $50(daily).
Those days I also started to a new game with some friends from my former company. I had written an rts game engine before. I prepared a level editor and some friends helped me about creating levels, graphics and sound in their leisure times. My first two games were prepared with simple graphics and simple mechanics, this game was an attempt for the upper class league. Of course you can not expect so much under these conditions, a few people trying to prepare something without any payment. The thing we get at the end was not that bad but it did not achieve any success. Rather than the game itself, this is more of a market issue. Google play has some serious visibility problems for unknown developers.. It didn't took long for my friends to loose enthusiasm and the game is left with only a few levels now. So the very few players who download it, finish all the levels within a short time and don't come back. Currently it earns a few cents daily.
... and my current status; As you would understand most of my revenue comes from the three online card games. Their total download is more than half million and they serve more than 1M daily ad impressions with 30 sec frequency. They make around $45 on these days.
But there are some unexpected movements on the former games in the last few days, especially in the billiards like game. It makes more than $5 nowadays and 2 days ago it made $13. The other game, air hockey, is not that well in terms of revenue but its download number started to increase, these are very recent changes. There is not stable numbers yet.
Probably many of you are reading this to be a criteria for you so I should mention a few things; my situation is very different than a standard case. If you can achieve 1M ad impressions daily you would probably earn at least 10 times more than these numbers. There are different factors that reduces my income, the most important one is the location of my users.
There are many different companies which offers different kind of monetization or promotion models, and some reach you through your apps. It is possible to find a suitable one which will double-triple your income. but it requires so much time to evaluate and try different offers. If you have time to invest(I have some serious issues on this part) it is possible to achieve nice results.