Right now I am in Lezno, Poland. For this trip and previous trips I purchased an International Data Plan from Verizon. The cost is $25/100 MB. I have gone through 100MB and have used 26 MB of the second 100 MB increment.
By the time I get home I am guessing that my data cost, from Verizon, for my phone will be around $75 for eight weeks. If I did not sign up for this plan my cost would be over $1,000. I check my usage and charges every few days.
If you have International Calling your "Anytime Minutes" or monthly allowance IS NOT DEDUCTED. You are charged .99/minute to $2.99/minute, depending on country, for voice calls. You are also charged, on Verizon, .50 for outgoing texts and .05 for incoming.
I am expecting a total bill of around $400 for eight weeks in Europe. This includes my normal allocation for three phones, 2000 minutes, unlimited domestic texts and domestic data. The International charge will be about $250 of the $400. The voice calls are what cost the most.
This is for Verizon only. Other providers may, and probably will, have different rates and plans.
On the ship you are charged $2.49/minute, for voice calls, no matter what plan you have but data was covered under the International Data Plan while on the ship.