Are Sweepstakes worth the Money

From the day I started working with online data I was told "Sweepstakes are worthless". Yet I have seen more Marketing sweepstakes come and go in the industry than I can count. I mean there are specialty companies that create sweepstakes and they are really profitable. The company isn't putting up the money for the prize, they are just producing the site and fulfilling the prizes, the client is coming up with the money. So, are companies seeing real returns for their dollars? I can't speak to my data but looking at the press releases and other sources it appears that sweepstakes do generate awareness about new or reborn products and yes have attributable sales to them. The only thing I would like to see is did the consumer enter the sweeps to "get a chance to win" what they already planned on purchasing? I will continue to scour the blogs/posts/PR to find the answer because to me that is the real question not, did anyone that bought my product enter the sweeps....