There's a point of diminishing returns to increased income, and it's personal. I have a family, yet I took a job paying less than the previous job because it was enough money and I really wanted to work there. Later, when my wife was unhappy at her lucrative job I encouraged her to switch to a lower paying position at a different company where she wouldn't be so stressed. We still make enough money, and our children are happier since we are happier.
The "don't care about money" thing isn't really true; you must care about money to some degree. But there are people who would rather do things that make them happy than always go for the biggest paycheck.
It's really I don't care about money after taking care of expenses and having a little left over to splash out every now and then. I think it's more commonly used in terms of the engineer deciding between $100k and $200k under vastly different conditions than the engineer deciding to work for free or very low pay.
The "don't care about money" thing isn't really true; you must care about money to some degree. But there are people who would rather do things that make them happy than always go for the biggest paycheck.