I've thought the same the other day when I've been pricing to a refresh on the bushs etc. Didn't realise myself there was 2 types. Most likely the same just different numbers on them.
It's £90 for the threaded insert or £175 for the full lower arm. Surely makes more sense just to get a new arm. For the sake of £85 your not having to chew on trying to get them out and the rubber insert mounts will be new as well.