Not all of them. Only some highend models. I remember some Sony 21" Pro CRT tubes that were less than 1000.1 some were even 300.1. Don't get me wrong im not saying that a LCD has the same or better black levels.
depends on the age of the monitor aswell, my fw900 (2001 Model) Id say is definetly less than 50k:1 probably 10k-15k:1