The biggest revelation for me was finding out about air credit, back in the days when O charged a deviation fee to fly in a day or two early. It's often a surprise to me how much the "free air" usually costs.
On our upcoming cruise we wanted to take the excursions as best use of the O life benefit. Unfortunately, I learned from the roll call, that included shore excursions were mainly full, so we opted for OBC. Then I did the maths! Choosing the drinks package works out at just under $27 per day, as opposed to $39.95 if we bought it, and having just a couple of glasses of wine per day would run to almost $34 when you include gratuities. We like wine with dinner, so I asked my TA to make the change.
Something that astonishes me is the price of a post cruise hotel booked through Oceania. They offer a post cruise hotel for £299 pet person, so £598 for us, for a standard room. I've booked a superior room in the same hotel for £159 and change. I know we'll have to organise our own transfers but we can take a taxi or a shuttle bus.
That being said, I don’t think paying $300 for $300 onboard credit is a rip off, it's just like paying ahead of time, and we never book that far in advance, post pandemic.