I don't know if I entirely agree with the "incredibly expensive" part. Unlimited bandwidth and diskspace hosting packages run around $20 bucks per month with some service providers (eg: Hostgator). I'm suspect the banner advertising program at the top of the pages more than covers the hosting costs and domain name expenses for a year. But let's face it, the owners want to make $$ - thus the Google Advertising you see and the strict rules on self promotion for vendors.