I am one of those odd people who thinks that the value of a business has much less to do with how much is currently being made and much more to do with future potential and what the new buyer can do to it with little effort.
For example, a site can be getting millions of visitors but might not be well-monetized and making practically nothing. A buyer can slap Google AdSense up on the page and instantly earn a five figure a month income (on a site that was previously bringing in $0/month) with about 3 minutes worth of effort.