I would think that how much, if any, a person cries is highly dependent on their own personality. I wouldn't think that you could quantify how much is "enough" crying. I was a cop. I don't cry. Ever. I have a hard enough time verbally expressing emotions in therapy, much less crying! It doesn't mean that I don't have any feelings, it just means that I don't express them or release them through tears. My wife is the opposite. She cries at the drop of a hat. I think just thinking about crying makes her cry!
So don't feel bad if you can't shed tears. Sometimes people don't.
So don't feel bad if you can't shed tears. Sometimes people don't.