The Giants signed Matt Cain to a 6 year $127.5M deal. Is he worth this kind of money? No, probably not. He did amass 5.2 fWAR last year and if for some reason you think that is his new baseline then one could probably make an argument in his favor. But let's keep in mind that he did so putting up an unsustainable 0.37 HR/9, 70.6 LOB% and a low BABIP against of 0.260. The Giants bought high on Matt Cain. Let's take a look at three of the main skill stats (K/9, BB/9, GB/FB) that a pitcher can control and compare Matt Cain to his recent peers. The comparison will not take into consideration age, as I am just looking at current skill comparables. I looked at 2010 and 2011 data only.
So, not exactly a stellar group of comparables. Good but not elite or record breaking good.