I guess I'm just looking at the guys they signed as FA's. Fielder, Upton, Zimmerman, Nathan and V-Mart are all terrible and I suspect they'll soon regret that Miggy deal. You say Sanchez worked out fine...he gave them one GREAT year, one very good year and now he looks like he's done. 3 of the 5 years will be lost in that deal + he has a $5M buyout on his option year.
I don't think their spending has been the reason they won 4 straight division titles (you could argue that signing/keeping their good young players was a key factor, as was stumbling upon JD Martinez, somehow getting Kinsler for Fielder, etc.). It certainly appears their heavy spending may be the reason they struggle to win for the next decade.