well, since it is a commercial website, it must be selling
something or providing something for the users. the something may
be free to use inorder to attract more users. and since it is free,
the owner will not earn anything right? so it needs advertisers and
sponsors to survive. and if you manage to get many and big
advertisers and sponsors, i can say you will earn big
profits!
you can go and find out the average advertising cost on popular
website. it is a few thousands! in this case, you have already
gotten back the cost with one advertiser!