Actually, it costs Cox to have Usenet on tap, because their Usenet implementation has been outsourced to Highwinds for years.
It's moderately annoying to lose it, especially as the overall price won't drop, but what's been lost here is actually no great shakes -- there's low caps on both connections (4) and speed, and the retention is 30 days if you're lucky. No SSL either, which has become pretty standard.
Yes, it means paying for an alternative...although it doesn't have to be Giganews. Astraweb works very well, and is fairly low cost on their unlimited plans, and if Astraweb is too costly and you don't care about posting access, there's Cheaper, which has plans starting at $4 a month the last I looked.