They charge per drink, but Carrie's right--it can save money if you're not doing an open bar. Right now, we're having the soft drinks package, bringing our own champagne (we have to pay Disney a $22 corking fee + tip for what they'd charge), and having mimosas ($9.50 per drink, I think). We're also debating adding a second drink, but if it's the same price, it won't be more expensive (unless people decide that instead of one drink, they need to have both....). I'd say having a signature drink is worth it if you're not doing the package bar, but probably not worth the extra cost if you are.