Damocles, I fully respect you as I know you have alot of experience in RTS development, and I also understand that thereare many variables to consider when asking how much a game should cost, and how long it should take.
I disagree though, because I think that a RTS like C&C should take no more than 6 mnths - 1 year for an experienced, dedicated individual, and it should probably be very cheap to make. Your costs would be a years salary(because there is no way you could do anything but work on the game for about 50-60 hours a week), your social life (you would need to limit yourself to maybe 1 nite a week out, or with your partner), and the basics (engine, cheap tools, etc.)
IMO, a RTS can't be that hard to make for someone who is equally good at modeling, and programming. You would need to plan everything out in advance, and stick to your gown guidelines.
I think Firoball should think about doing this himself, as I feel not only is it the most rewarding experience, but also the best way to learn. I feel this way because I have done the same thing, but at a disadvantage. Before January of 2007 I had zero programming experience, or 3d graphics experience. I am nearing the end of my project now (a rather large RPG), and have done it almost entirely on my own.
My belief is simple, if you stay dedicated and meet your own goals, you will finsh anything that you set out to do.
Best of Luck!