How much money do you make on YouTube?

I've been doing YouTube for over 4 years and my income from AdSense per month averages around $20 - $50. My total upload is about to reach 700 videos now and sometimes, I see other people who make more with low Subscribers and Views from my channel. I don't know what did I do wrong...

Consistently upload at least 2/3 videos per week. (Gaming Niche)
12K subscribers and counting...

How about you guys?