Seth has an interesting article, Rights and responsibilities. The article talks about where your bottom line comes from- is it from taking advantage of the poor and uneducated or is it to bring joy in a bottle.
Do not take advantage of a hired man who is poor and needy, whether he is a brother Israelite or an alien living in one of your towns. -Deuteronomy 24:14
To me it comes down to what “advantage” means to you. I don’t know where to draw the line, but if excessive use of your product or service kills your customers (even if it takes decades), I would say that is a poor business model.