Unfortunately there's a lack of reliable data, but from the offers I've heard, of my guess would be that someone making 100K in Austin would be making 50% more in SF, and possibly making double if they got lucky. That may in part be due to my familiarity with the area though, but again, I know more people in SF making 200K as right-out-of-college-kids than I know people making 100K in Austin.

As far as Seattle goes, I think that the state tax makes up for most of the comp differences, and housing is cheaper there, so its a better value if that's all you're optimizing for.