Just as it is with almost any other business on the internet, online casinos are looking for sponsors in an effort to help to defray the costs that they will face. This is true with almost anything though. The online casinos will ask certain companies and other entities to pay money for the privilege of being able to display or promote their product somewhere on the site. The other thing that companies will try to do is to get a link to their own site at the casino. In many cases, this will cost the sponsor a great deal more, however, it will pay for itself if the casino is generating enough traffic and business to your site through theirs. It is a matter of if you are making a wise business choice or not.
So, next time you go to visit your casino, you may want to check out one of the links as it may help keep your costs down as well.