I'll give it a shot... don't have the CFI but I'm working on it so I do have an estimate for myself.
Supposedly the average is something like 50hrs ground and 20hrs flying. My instructor, however, finished his CFI in 16hrs ground and under 10hrs flying, and I'm hoping to do the same.
The key, as I've been told, is to study, study, study, and practice teaching at home. If you go into the training well versed in all things flying you'll progress much faster.
So the answer is that the average 50*35 ground + 20*100 flying complex = 3750.
If you do it concourently with another rating and / or study hard for it you can do it around 20*35 ground + 7*100 flying = 1400, less than half the cost.
The way I look at is I can pay the guy 35/hr so he can spoon feed me the info, or I can do it on my own and show up very prepared and ready to teach. Of course you'll want to talk to your CFI prior to starting so you know exactly what to expect.