I have just returned from the Italian Delights cruise on the Sea Princess and hope to do my review in the next few days.
It cost $3.90 for spirits and mixer, $3.25 for a Bud Light, $6 for a 750ml can of Fosters, cocktail of the day was $3.25 small, $4.95 medium and $6.50 large, a glass of wine ranged from $4.50 - $7.00. I think a 1/2 pint of draught Stella was $2.25.
You can purchase a sticker which allows unlimited fountain soft drinks, not cans, for $49 for 14 days.
Didn't buy any bottles of wine so can't comment, but you can purchase your own ashore and pay $10 corkage if you have it in the restaurant.
HTH
luci