Progression to the Margin?

The following text is taken from a book written by Todd Buchholz titled New Ideas from Dead Economists (from chapter VII "Alfred Marshall and the Marginalist Mind"):

...Imagine you are traveling through Europe.  You begin in Greece and have a splendid time.  On the way to Italy, you stop in Corfu, where you rent a moped [and admit to it?] and circle the charming island.  In Italy you enjoy Florence more than any place you have ever seen.  Your visit in Italy cost $800, but gave you thousands of dollars' worth of pleasure.  You reach Venice and then consider crossing the border into Austria.  Austria, you fear, will be disappointing compared to Italy.  You prefer calamari to Wiener schnitzel.  How to decide whether to go forward or go home?

First, consider Buckaroo Banzai's advice [an earlier reference in the author's chapter]: "No matter where you go - there you are."  You are now on the border of Austria.  Forget where you have been - the pleasure you had in Italy is irrelevant!  Marginalism declares that the past is behind you.  The issue is whether to step forward, and the starting point is where you are now.

Second, think of Henny Youngman's joke [again, an earlier reference from the author in the chapter].  What do you compare when choosing whether to go into Austria?  You ignore the past pleasure in Italy and ask, Will the benefits of going to Austria exceed the costs of going to Austria?  If a day in Austria will cost $50 and give you $75 worth of pleasure, go.  So what if in Italy the benefits outweighed the cost by tenfold?  The issue at hand is whether to go forward.  And you should go forward if the benefits outstrip the costs, even if they exceed by a lesser margin than before.

Third, remember the editor in Scoop [yet again, an earlier reference].  Up to what point do you continue moving forward?  You continue as long as the benefit of one step outweighs the cost of one step, until the marginal benefit equals the marginal cost.  When a $50 day in Austria gives you $50 of pleasure, you rest...

So, I'm not sure what this means in regards to which infielder a manager should give more playing time to.  I'm guessing that this is only relevant to deciding where to go from here based on whether your decision's expected benefit can surpass its expected cost.  Now, when it comes to making decisions based on playing time, all this crap - well, most at least - goes out the window and a determination has to be made as to who will provide the most benefit above cost [cost being, in this case, the loss of playing time of another player since salaries are going to be paid regardless].  And, well, if you as the decision maker expect infielder A will be of more benefit to the team by taking at least some playing time from infielders B and C, then you do so...even if B and C are generally regarded as better; and only if a benefit for doing so is expected [reiteration for effect].  But, be warned, fan[atic] A, B, and C will be critical of your every decision: for the fanatic really believes that s/he is a better decision maker than you...and believes this by a wide margin, too!