That's normal for internet at sea since it's through a satellite network that everyone on the ship and everyone using the same satellite has to share. You can buy a bucket of minutes that will save if you plan to use it often. If you want to save just visit a coffee shop in port that has free wifi.
11 cruises in 2012, 90 nights at sea visiting 15 countries
8 cruises in 2013, 56 nights at sea visiting 7 countries
Next cruise: None scheduled
PM me if you need a cruisemate for any Europe, transatlantic, or Panama Canal cruises
Date, ship, cost pp