Being nice helps.
Me being nice today saved me about $75. As I was checking my luggage at the airport, I engaged the check in lady, made some small talk, asked her about her vacation, and was polite.
The result? She didn’t notice / didn’t care that my bag weighed a few more pounds than the “standard rate” weight. If she did notice or did care (which would have been more likely if I was rude to or ignored her), I would have had to pay quite a fair amount of money.
Moral of the story: be nice to people. Chances are, it will never hurt you to be nice to people.