There is a wine package and there is a soda card. The wine package is for 5,7,10 or 12 btls, and for each there is a Gold, Diamond or Platinum option. Prices and sections are all on the RCI website under Deals & Gifts > Shop Gifts & Gear > Wine & Dine.
They charge you a corkage on any bottles bought on the ship.
To correct mr Laird's post - you are NOT ALLOWED to bring any wine on RCI. There is no such thing as a corkage fee.
We found the wine package was great, we paid £201(platinum package) in advance for 12 bottles, when the waiter at dinner or in any of the bars you might want wine brings you the wine list to order you hand him the card showing you have this package and it gets taken from the card. This is the only way you can take bottles of wine to your cabin, and if at the end of your voyage you have bottles left from your package they give them to you to take home.