Are you saying that Santana earned his $20+M? Sure, IF HEALTHY, and relative to what other top SPs make, he is worth $30M (or $33M considering they probably could have gotten him this year at $18M through arbitration).
BUT....
Pitchers health is a difficult thing to wager on. Since the 5-man rotation about 30-35 years ago, how many pitchers have made 7 consecutive seasons with 30+ starts? I doubt very many. And that is ignoring whether or not all 7 were good seasons. Sometimes pitchers get a nagging injury that they are able to pitch through but it makes them ineffective (Lincecum).
If you can afford it, which the Dodgers can, then yes it was probably worth it, since he is hands down the best pitcher in baseball and young. But it's not a deal the Reds, Pirates, Brewers or probably 2/3's of the MLB teams could make.
I'm just surprised that at $30M the Dodgers allowed him that opt out after 5 years (but they don't have an opt out).