Probably the best article I've read about this topic. I see this in pretty much every negotiation I take part to, especially the larger ones:
I could sum up my negotiation mentality as a seller in one phrase that I’ve used as short-hand for my portfolio companies for years, “Everybody wants their pound of flesh.”
It’s short-hand for showing that despite our aversion to the process of negotiations – as buyers we’re conditioned to it and even rewarded for it.