Well, this is really a very broad question to be replied, It just depends on various other factors like what ads network are paying users? etc.... etc.... you just can't guess the income just by seeing the downloads. But still if i had to say then i'll say $5000000........
I'm going to guess it has a lot more to do with how much they get from the ads than anything else. If it's an app that shows ads often then the developer will get more than if it's an app that usually works in the background and rarely shows ads.