The problem is that just paying higher salaries would not necessarily correlate to increasing the supply of
good developers. The sort of developers who only come in because you're paying 200k rather than 150k are usually not the sort Google wants to hire.
So the supply will increase, just of lesser developers. Additionally, I think it is possible to pay developers too much: I recall some study about how a salary beyond a certain point can actually make developers less productive. (I could very well be mistaken on this--I'm too lazy to go look right now.)
Basically, trying to hire great developers is complicated and just having more random people go into software is not the answer. Software is already one of the best paying "hacker" jobs around anyhow; you're not likely to attract true hackers based on more money.