i haven't seen any cost-effective low end jukeboxes.

we used one or more big ultrabuzzword2 scsi discs with a pseudo-worm.
i still do that at home:  http://www.caldo.demon.co.uk/home9.html.
it's not foolproof but it does well.

choose the same block size as you'd like to use on a real worm jukebox (when you
get one).  it's possible to copy the pseudo-worm to a real one (i used a specially-modified
file server kernel for that), so that if you get something fancy later you needn't lose all the history.