Depends on what you consider "worth the cost"
Free is nice, but I'd gladly pay $2k for a chat program that does what I need. Kayako is nice in that I can monitor chats in real time with employees and managers can jump in if needed (or provide assistance), but there's other parts that are limiting.
I was able to view the transcripts in LiveZilla but wasn't able to do searches etc
I know they're coming out with a new version (currently in beta) so maybe it'll change when that releases.
But for a free program, LiveZilla beats many other chat softwares that are out there.