MMORTS

Well for about 2 years now ive pondered around trying to learn C/C++, and 3D Modeling. Ive gotten far, atleast seeming to me as far. And ive come up with a game idea for a MMORTS ( Massive Multiplayer Online Real Time Strategy ). Mainly im just wondering how much it would cost to have something like this made. Id like for the server to be built for a MS Windows or Mac, And the client for both Windows and Mac. Mainly it will be a close Command & Conquer type game but also intertwined with Space. Different planets to play on, Add one everytime they are full. Players can travel between them. Login interface on both Client and Web Page. Im also wanting Web Page support, So users can login edit their login, buy a subscription, have forums to talk on. I'll get more into detail later on. But mainly this is for just to see how much it would cost. The AI for this may be rather big, Because there will be Alot, Alot of "Units" to be controlled within the game. Thanks for any bids, Danny.