So what is the best way to overcome the "I don't want to pay for it" argument when trying to sell people on the idea of using Usenet?Ah, but people are paying for it. They pay with their time and interest in the subject-matter. Their time has value. Their knowledge has value.
This "paying for it" mentality has arisen with the commercial takeover of the Internet. Back when the Internet was young, there was a completely different mentality. It was a 'How can I help the next Man?' mentality. It was quite literally an 'open-source' mentality, and that was because the early Internet was not the domain of the commercial interests, but the domain of the universities and other centres of advanced learning.
My earliest leafnode of Usenet was as an offshoot of the Adelaide University in South Australia. I was part of a UUCP 'store and forward' sub-network. I remember the excitement around 1991 or so when the buzz was that there were now a million nodes on the Internet(!).
I also prefer a TUI/CLI client.
When you're using pure text 99.9% of the time, you might as well use a text-based client. If you have a 'Desktop GUI' you merely run that text-based client in an xterm.