Many of these websites pull people to their web site by getting huge friend lists on MySpace and them spamming out the URL in bulletins and messages.
Yahoo! recently banned several of these websites from their advertising network for having poor quality traffic.
When you think about the amount of time you have to spend getting friends and promoting it everyday and the actual amount of money you are bringing in... ehh
No they aren't worth it. Why would they sell these packaged sites for $50 if they were worth it?