So i figured i'd answer my own question: what are port fees? What i found on Fraud-Lawyer.com was very interesting:

"Large cruise lines have been over charging people for port fees but illegally calling them port taxes. Since there are no port taxes suits were filed against almost every major cruise line. The cruise lines offered discount coupons or voucher compensation instead of monetary compensation while renaming their illegal fees to port service fees. One cruise line, Royal Caribbean/Celebrity separates the fees as non-commissionable cruise fares on the invoice to travel agents and had sent a letter to travel agents instructing them to avoid using the term port charges if speaking with customers."

"Many people believe that the mysterious charges are simply a way for cruise lines to create a profit center. Port charges have continued to rise over the last several years, and cruise lines have countered criticism by claiming they have simply been responding to increasing rates. The truth is, when trying to receive information from cruise lines about the breakdown of the port charges and fees, the cruise lines would rather lose business than to disclose this information."

I see now that it's very important to find out as much as i can about port fees before I book a cruise.

Here is a link to the page - http://www.fraud-lawyer.com/html/pfraud.html