We spent $125 at Publix before boarding last week (thanks Dave from Marietta for the directions). We had to buy baby food, formula, diapers, water (for formula), bottled water for us, Diet coke, bibsters (which worked great), crackers, etc.
We didn't want to pack all that and bring in our suitcases on the plane. It worked out well for us to stop there. Ended up we didn't have enough room in our 'extra' suitcase, so I got a box from the store and put the items in it and the guys at the ship taped it up for us. Very nice of them.
We were glad we did that because they don't sell too many of these items on the ship and if they do they are priced like gold. Example - $3.00 for one feeding of similac instant formula.
Good luck.