Ok, several points. And this is coming from someone who has been in the website/advertising business for 23 years.
1. It's very difficult, if not impossible, to run a profitable news operation like ZH these days on Google ads alone, especially considering that they only get paid when users click on an ad. It's obvious right from the start that this is true because the first thing that ZH is offering in exchange for the subscription fee is no ads. But the important question to ask is... when is the last time you visited ZH and also clicked on an advertisement you saw there? The answer is probably never. So your value to them as an occasional lurker is essentially zero. And there are probably a lot of people like you out there.
2. You can't compare the monthly subscription cost of a service like Netflix to a monthly subscription like ZH because Netflix is a mainstream service, meaning that everyone on the planet can find and enjoy content on Netflix. They can afford to keep the price low because they make it up on volume. Last time I checked, Netflix had almost 200 Million subscribers. The market for a paid niche news service like ZH is nowhere near that big. Not even close.
3. Financial and political news is everywhere online, so ZH has tons of competition out there to deal with. So realistically they can only expect to capture a small percentage of the overall demand, especially since a lot of the news available out there is still free for end-users. The Wall St. Journal is an old and respected publication so if anyone can make the subscription model work before anyone else, it will be them. But again, the WSJ is competition for ZH, and the only way ZH can compete is if they can publish niche articles that provide content that the mainstream media doesn't provide. But unfortunately, the more niche a publication becomes, the smaller the audience becomes. So that's why you see the higher monthly prices they are wanting. It's really the only way that the business model works when you consider the fragmented and small size of the market they are going after.
4. The primary reason you are seeing so many blogs and news services moving to a subscription model is because Google and the other ad networks are essentially black boxes. In other words, Google takes a significant cut of the ad revenue and then passes along whatever is left to the publisher. But the publishers have no idea how much Google is scraping off the top, but it is significant. That's why you see Google raking in billions and the blog/news publishers are barely able to survive and thus need to switch to a more profitable model of doing business.