As someone who is making a living doing what I love, I really like your points about the specious connection between making a living and losing your focus.
I do, though, think you are overstating your point. There is no doubt that in my field (science) many people are motivated by issues of money rather than issues of love. It doesn't ruin the field, and I wouldn't even say that it was most of the people, but it is a danger than every scientist becomes aware of and comes to terms with. I think that, similarly, in martial arts that are more easily commercialized (like TaeKwonDo, for instance) teachers know that they must learn to walk a fine line. I don't think there is anything wrong with facing these sorts of dilemmas, and I think they can even be healthy for the sensei and his own understanding of his art and his way, but they are always there.
To me it often seems like there is a simple rule of thumb: the more money is involved, the more you will tend to find people around who care about the money. On the other hand, there is another issue to deal with: the more you expect people to live off of thin air, the more you attract a certain confused kind of person who believes that's really possible. Not necessarily a good thing, either.