I had a quick look myself, as I found the figure interesting.
According to Uber[1] an UberX driver in NYC averages almost $91k per year based on driving a 40 hour week. However, in a follow up by BI[2], this figure seems to be widely refuted by Uber drivers across a number of states. For example, one in NYC says he drives 40 hours a week and doesn't expect to take in $50k this year, but that you can clear $4k a month after Uber expenses, gas, etc. doing 40 hours without too much hassle.
1. http://www.businessinsider.com/uber-drivers-salary-90000-201...
2. http://www.businessinsider.com/how-much-money-uber-drivers-r...
It does offer more benefits than just pay though. I mean you get to choose your own hours, can work as much overtime as you like, comparatively low responsibility, etc. If one could get $90k-$100k out of it with 40-50 hours a week, it would certainly be attractive.