There's a sabermetric case to be made that the Choo signing is a decent deal by FA standards. He's been worth the $18.5M he'll be getting in 3 of the last 5 seasons, and that's before accounting for the current FA inflation and the fact that he's probably worth more to the Rangers than he is to the average team given how well he fills their LF hole relative to their alternatives and where they are in the success cycle.
Like almost all FA, he's going to be overpaid on the back end of the deal, but that's the nature of FA signings, which you can only really afford to make a big splash on if you're simultaneously underpaying a lot of your young talent (which is also the nature of the game).
My point was that the comparison of Choo to Cabrera/Mauer/et al that I quoted above wasn't a sabermetric one, so if that's what you're seeing to justify the contract it's not fair to disparage those arguments as sabermetric rather than as poor use of traditional statistics.