Anecdotally: as long as I don't go during rush hour (i.e. 7-9am or 4-6pm on weekdays), I can get from anywhere in the densely populated sections of Chicago (basically, anywhere within 5 miles of the loop) to another section for ~$3~5 via Uber Pool/Lyft Line. At that price point, it's competitive with taking public transit.
I'm interning in Chicago this summer and I've already taken pool/line 10 times, each for ~$3~4 and taking ~20 minutes and going about ~3 miles. Uber/Lyft's algorithms for matching riders up is actually pretty good in my experience, but even then let's assume that each driver has two riders per trip, each paying $4 and each trip taking 20 minutes. In which case, they'd have 6 riders per hour for a total revenue of $24/hour before Uber/Lyft's cut and accounting for their own expenses. I refuse to believe they can actually make a living by driving this way.