I found the following on Carnivals web site under FAQ
There will be a one-time activation fee of $3.95. CruisE-Mail is $3.95 for outbound e-mails and sending a 20-second video postcard will be $4.95 with e-mail included. The cost to print information is $.50 per page.
Internet service may be purchased on a "Per Minute" basis, or there are two "Block Packages" to choose from. The "per minute" charge is $.75. However, you may choose Block Plan 1 at a total cost of $55 for 100 minutes ($.55 per minute). Block Plan 2 is $100 for 250 minutes ($.40 per minute).
Charges for this service will be billed to your Sail and Sign Card