Y'all should probably post how many sites you are running to make it a fair comparison. I highly doubt anyone is bringing in $100 a day off a single site. Also might consider comparing how much you are *spending* to bring in that kind of traffic in the first place.
There are a lot websites that were well established and profitable before adsense came along.
As jomaxx mentioned, not everyone pays for traffic.
I have a site that makes over $100 per day without any paid traffic. I'm sure I'm not the only one in this position.