It depends on the sub-niche that you have, I mean, the sports niche is very wide.
Generally speaking, that niche doesn't pay as well as legal insurance, certain medical niches and certain types of services and software.
But even in such a niche as sports, you can find a sub niche that would pay a little bit higher.
It also helps that your visitors are from tier one countries.
When you mentioned 50,000 to 100,000 per month, are you talking about pageviews or actual visitors?
These are two totally different things.
As you probably already know, when it comes to AdSense, you need to maximize your pageviews.
You need to get every single visitor to your site to view as many pages as possible.
There are all sorts of tricks that you can use to make this happen but you need to focus on page views.
Given the amount of variables in play, and the fact that you didn't really give much details, except for some rudimentary traffic, and niche figures, it's anybody's guess what you should expect to earn with AdSense.
What I do know as far as my own experience goes is that even if a site doesn't get much traffic, as long as you're in the right niche, and you pay close attention to page views, you can make decent money.
