This info comes from Gamespot:
Sega has announced that it plans to implement a flat rate for consumers interested in playing networked games over the company’s SegaNet online service. As of November 1, the company will charge $9.95 a month for unlimited access to Sega’s online multiplayer games, as well as features such as instant messaging, profile pages, and organized online tournaments. Starting November 1, existing SegaNet customers will have to pay to access the service. The flat rate covers every online Sega game other than the original Phantasy Star Online, which the company said would still be available for free because it runs on its own servers.
As announced earlier, the SegaNet service will be rolled out across all upcoming and current platforms, including the Microsoft Xbox, Sony PlayStation 2, and the Nintendo GameCube for online games. It will continue to support Dreamcast games. The SegaNet ISP service, which was originally introduced alongside the launch of the network, was discontinued in July.
Source: Gamespot