Think about it in terms of opportunity cost. Money spent on one thing cannot be spent on something else. Saying "this is always more important than financial gain" in effect means "this is always more important than everything else". That's clearly a form of taboo - you're rejecting outright the idea of trade-offs between competing values.
I guess I'm interpreting wrong because that is obvious and there is nothing taboo about it (cultures will be different re. taboos anyway).