“Either it is legal or not.”
Is it really so black and white? May I suggest any number of works written by Rav Ahron Levine Z’l.
Econimics and Jewish Law, or perhaps Business Ethics in Jewish Law or perhaps Economic Morality and Jewish Law (among many other books he wrote).
I am not here to pasken, but you will see that it is not so simple. Where does “hin tzedek” (your “yes” should be sacred) come in to play. What about Vihyisem Nikeyim? Geneivas Daas? These are not abstract concepts.