I rarely spend more than $200 extra and cruise ALL THE TIME lol.
Think of it this way; I'm sailing on Oasis for a week, already booked. Friend wants me to commit to beverage package $50/day plus tips. Instead I will get off the ship, change over to the Epic, and sail an extra week. Same cost basically. And that's one add on, think of how many trips you could take had you not gambled or spend hours in the spa etc.