At the same press conference in which Square Enix USA announced the late-October release date for Final Fantasy XI For Windows, they also revealed the pricing information.
Final Fantasy XI subscribers will recieve their first month of play free. After one month, we will be charged a starting fee of $12.95/month. We have the option of adding the Tetra Master game for an additional $1.00 per month, and can add additional characters to our account for another $1.00 per month.
Square Enix also confirmed that Final Fantasy XI For Windows will retail for $49.95 and will include the "Rise of the Zilart" expansion pack. They also reiterated that the Playstation 2 version will be published by Sony Computer Entertainment America, and will be released alongside the launch of the 40 GB Playstation 2 Hard Disk Drive, which has yet to recieve a specific Q1 2004 release date.
Source: Square Enix USA, square-enix-usa.com