Usenet used to be freely available through most ISPs. But now, even though there are still a lot of usenet groups active for discussion, it is also used for file "sharing". So hosting Usenet groups can be very data intensive, and ISPs stopped hosting them.
Google hosts a free portal into usenet at groups.google.com , but I just went there and saw that even they decided it's too much trouble and will be stopping soon.
There are a few subscription based usenet servers, they vary from $5 to $10 a month. Easynews.com , giganews.com are two that seem to still be open.
Yeah Google bought a really great thing and ran it for a very long time as their own version of stackoverflow. I bet stackoverflow was a response to Google’s monopoly on groups answering questions.
I think Stack Overflow was a response to Experts Exchange which teased you with a question but you had to buy a subscription for the answer. Subscribers would answer questions and pay for the privilege of providing that site with content.