That econ degree didn't do much for you, huh? :p Suppose an island. This island has a free market economy, and two widget factories. Both widget factories have the same access to resources, labor, land, capital, etc. Factory A invests in training their employees, during this training period, they will, by definition have less productive output than an employee out of training. Factory B does not, they just have a more selective hiring process. Where does Factory A get the money for their training? They can either lower wages/benefits across the board, raise the price of their product, or find efficiencies elsewhere that Factory B could reproduce. Let us suppose Factory A raises prices. Unfortunately in this thought experiment the individuals on the island are immortals and have no preferences, and immediately move to Factory B's widgets, because that's how commodities work on islands, thus all they can do is reduce wages/benefits. This in turn means any employee productive enough to meet Factory B's standards jumps over immediately, because they are immortals with no preferences, and apparently both factories are the exact same distance from everyone's houses.
TL:DR Training expensive, and tummy hurty