You know those online competitions where you have to choose three numbers out of a list of about a hundred, and if you get the right number you (supposedly) win? They do it a lot on the webpages of interiors magazines. Obviously the range of possible numbers are so huge as to make it more or less a certainty that no one will win the prize. So the company providing the prize save money by not actually ever having to provide a prize presumably, as no one will win it. And they must do it as a form of advertising, in the hope that you will see the prize and then be interested in the product.
But what do the host of the competition get out of it? So, eg Ideal Home magazine, which is where I see this a lot. They have to host a website, and host the competition on the website. The competition runs for months and they presumably have the costs associated with that. And thousands of people are entering random numbers into a number generator thing for months on end. But...what do they gain from that? I'm intrigued.