由還錢談起 (To repay or not to repay -- that is the question)

由還錢談起 – Yes ... my dear friend lost in contact, I am thinking about you... and, to be specific, the money I lent to you some years ago

Prof. Jerry Liu is proud to be a weekend vendor. I admire him and admit that I am too impulsive to do something like that. On the top of that, I surely will exercise the price discrimination toward customers. In light of that, I might do something on which I seem to have comparative advantage (to some extent). Here is what I have in mind. Twice in a week or so, I shall post some crazy (or naive) thoughts here as open questions or questions that demand serious follow-ups rather than cheap answers.
Here is the first one:
期盼友人還錢，真的比中統一發票還難。可是，很多學生卻能輕鬆地說：『老師教過的，早就還給老師啦！』(難怪老師不易瘦身？) 緣此，應該調漲學費。保留知識、不還給老師的人，日後可以部份退費。至於還給老師的人，既然豪氣萬丈，當然不必退費給他們。會計室是最大贏家。
forgot to add: 當政客貪污、醫生與教授舞弊新聞爆發時，民代、教育界、民意異口同聲，要求他們以前的學校(e.g., NTU among others)，應該對倫理教育負責之時，怎麼沒想到，他們只是把學的東西，早就還給母校呢？To me, it is not much different from the situation at which quite a number of students taking my economics or professional writing courses already returned whatever they learned from me. No big deal.
如果是我當家，也許在英語初戀營的宣誓詞，加上:
敬天愛人；學多少、算多少、Never repay!