You need to take the fx rate into account for us Brits. A single glass of wine on Princess, even at the old prices, is the equivalent of £12, when you take the 18% service charge into account.
Princess Plus costs £50 pppd, so once you have factored in the gratuities, "break even" is only around three glasses of wine a day. I would drink that number at lunch time ! Plus of course, soft drinks, coffee etc.
And the wifi is to all intents and purposes free.