You could buy a TV worth several thousand dollars and they'll still show you advertisements. Also in Samsung's case they'll take screenshots of what you're watching to find out what you like. There's always money in the advertising revenue stream.
Are you talking about smart TVs? Because ads only show up on real TVs if you tell them to. It's the cable you plugged into it or the ads at the beginning of the movie you just paid money for. It's not the TV. The TV is dumb as hell. It only shows you what you tell it to show you.
