I think most people are severely underestimating the potential with display ads. I have two friends with websites that get 80-100K sessions a month and both are earning anywhere from $30-40K per month in ad revenue alone (I've seen the payouts). Granted, these sites are not in the travel niche (which has lower ad rates at the moment), but...that's serious money.

Both Ben and Gary have to be generating at least 300K sessions a month on their blogs. At least.