To what emotions or values does Gradgrind appeal to while telling Bitzer to let his son Tom go?

Gradgrind uses every method and emotion he can think of in begging Bitzer to release his son. First, he asks him as a father; then he appeals to him as a former student, and lastly, he resorts to offering the man money as a bribe. If nothing else, we see that Bitzer has completely prescribed to Gradgrinds teaching, and that he adheres to the; "fundamental principle of the Gradgrind philosophy, that everything was to be paid for. Nobody was ever on any account to give anybody anything or render anybody help without purchase."