Having recently returned from a Princess Cruise, I did feel that the pricess are quite expensive compared to P&O cruises which is usually similiar to the average pub prices. I manged to get a few bar pricess with me so here is a rough example of what to expect onboard

Bottle of Beer $3.50
Bottle of Water $3.50
Soft Drinks $1.50
latte $5.50
Glass of WIne $4.50

I beleive you can get drinks packages onboard, but I am unsure of how to book those or what they cost.

I hope this information has helped

We did the panama cruise last year on the princess coral, if i remember correctly as soon as we boarded we were asked for a credit card to remove a total of approx £230. £43 was to buy the soft drinks package(free lemonade,coke and ginger pop) for 2 people for 10 days the rest was for tips for ships personell for the wife and i, there was additionally a 15% charge on bar prices for for tips for the bar staff.
i personally thought this was over the top and new that i could reduce the initial amount and was questioned by the purser why i did it ? i remarked when i am able to purchase the cruises on the cheaper american princess websites i will then reconsider the tips situation.
check for current position on princess website.

Thanks for the information, I have been speaking to someone who said the same. Nice cruise ships but beware of all the hidden charges! I was told about the 15% surcharge on all of the drinks, I will do a bit more homework before I make the decision! Thanks again.