“In Pirkei Avos, Rabbeinu Hakodesh teaches us a valuable precept:  ‘Calculate the cost of a mitzvah against its reward.’  Imagine that someone were to offer you a million dollars to abstain from wearing tefillin; you would surely turn it down.  If so, you should perform the mitzvah with as much joy as if you had received the million dollars!” ~ R’ Avraham Mordechai Alter zt” (Imrei Emes) from Torah Tavlin