That's a lot of money and I think only a very few are making that much. You need a new game with approximately 100,000 downloads each month to get a sum like that. Not an easy task.
Sorry for the confusion, I do 3d modeling for my main income and that's just way more steady than games making. But that has taken years to get that steady flow. I would think it would be the same for any business, there are no quick fixes just hard work and plenty of failures along the way till you know how it works. You have to look at how many people are doing this and how many out apps you have to beat for that dollar is this right for you how hard are you going to work to make it happen. One thing I have found you have to pay to get you're game noticed and put up in the rankings. It's not going to get off the ground unless you have a publisher. But I'm still figuring it out, and for now it's a hobby and I know it takes time to get the knowledge to be successful.