Friendship and money - don't mix.

This is proven by introducing money to monkey communities.
Monkeys were getting plastic tokens of different colors for their work, and behaivor. Different color tokens had different value. Blue one could buy a banan, red one several grapes, black one - could buy nothing.

Eventually, monkey were not interested in black ones, but would fight over other color tokens, even more, female monkeys would hang out more with those males, that had a possesion of more tokens in their corners...

Money can creat arguments even among monkeys, so friendship should be free of money responsibilities.