But if you are looking for an on-going relationship, this changes the dynamics and gets much more money than simply hiking your rates.
It's related to the game where one person gets $10 and then has to share it with another, who has the option of rejecting it. If they reject it, you both lose all the money. The simple game theoretic analysis is that you should offer $1. They're better off accepting than rejecting, so they should accept.
But they don't. Experiments show that people will reject any amount below $3, and $3 itself is marginal. People have an inate sense of fairness, and if they think you're not acting fairly then they will punish you, even if it costs them money.
There is often more at stake than the obvious financials, and this is an example where that is being recognised and used.
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