Software development is an art, it can't be quantified, aproximated, or similar.I am talking here about true software, wich does not crahes ,missleads or complicates life more than it already is.In the same way a tree grows, an application should grow too - branch by branch, leaf by leaf, without planning each leaf or even each branch. It grows according to the environment it lives in, adapting each step of the way. Since you can't predict the environment, you can't say when it will be fully grown.
Think about Leonardo or any other genuine artist:what would have happend if someone would have hired him to do "Monalisa" in say, two weeeks?
Well -=nice dream=- but what about the money?
This is quite simple-there are Low risk investments and High risk investments-software is a high risk one. It is the bussinessman's job to take risks and programmer's job to build application(s); not the other way around.
Of course, if a genious programmer is also a sucessfull bussinessman than the hole software world goes to hell, fast....