I'm usually reluctant to share any numbers, but it's a few dollars per month per article (on average). It adds up over the years and has been very consistent, which is why I like the segment a lot. Unique views is not a useful number in my opinion, it's all about total revenue. I suppose it's the hyper-local aspect that drives up the ad bid prices on Adsense. The content is also a great example of "Evergreen Content", unlike, say, a review of a World Cup game from yesterday.
I really see it as publishing my thoughts and notes, and things I would have liked to have known in advance. Typical entrepreneurial thinking, "Solve a problem that I actually had", but at a micro scale. Sometimes I end up reading one of my own articles in a few years time because I've forgotten the precise details of the process when I have to go back again.
(This has been one of my highest-upvoted posts on HN so far)