Conclusion
While the Cardinals haven't had the best shortstop in the last four seasons (or even the most valuable), they have been able to save money using the players their system has promoted. By avoiding expensive free agents and choosing to work with in-house players, the Cardinals have been able to save money that can be used in other places.
In the future, so long as the owners are willing to sign some checks, the Cardinals would find the most value for wins by dipping into the free-agent market.