The above-mentioned sources are mentioned by the poskim as the reason for making an extra effort to purchase quality tefillin. Since the expense is a one-time outlay and the merits and power of quality tefillin is so great, when parents buy their son his tefillin for his bar mitzvah they should make every effort to provide him with the best protection and honor he can get. As tefillin serve as a sign of their son’s Jewishness and G-d’s insignia, it is the most powerful tool available to enable their son to withstand life’s trials. When giving a bar mitzvah boy this tool, it should be of the best quality available.
In addition, the Gemara (Menachos 44a) writes that in merit of laying tefillin one earns longevity and health. This is learned from the pasuk: 'העליהם יחיו ולכל בהם חיי רוחי ותחלימני והחיינו - “O Lord on them [You said] they shall live, and before all of them the life of my spirit, and You cured me and gave me life” (Yeshayahu 38:16). When Hashem’s Name is upon a person, he merits longevity, a cure, and strength. Which parent wouldn’t want this for his child?
