Those coupons are not meant to be a value, rather a way for friends or family or perhaps a T/A (as a reward for loyal clients) to provide a gift for passengers as a bon voyage gift. The only benefit to buying one for yourself on a cruise is to get some of the expense of the vacation out of the way up front if you'd like. The daily specials without the souvenier glass are typically the best value. They're usually some kind of tropical fruit mixer (mango, pappaya, etc.), usually frozen, with rum or tequilla. A tropical name and often very good when you're heading to a tropical destination. They just kind of fit with the steel drums and other themes onboard.