Apple - Good Newsgroup Client for OS X

Unison by Panic is quite good. It's fully featured and looks nice but the UI is a bit wonky at times.

https://panic.com/unison/

Unison is very nice and freely available (but not actively developed). OSXnews may not be as polished as Unison, but it works and it is open source.

"Cheap" is a relative and subjective term, but if you want good, then I highly recommend Unison by Panic Software.