Metroid wrote:is it a magnet? Or just some sort of rubber seal? Either way, it has to add an extra cost to the price of the cup I would think.
Its a magnet. I guess the marketing solution they are trying to use to help alleviate the costs is to sell adds on the magnets or use them as promotional devices which is actually pretty clever. At the bottom of every beer get a magnet coupon for a free Dunkin Donuts coffee or whatever.