When two people are negotiating, but neither person really knows the value of what they’re negotiating, be sure to begin the negotiation by throwing in an extreme number in your favour.
The reason is that humans have a tendency to anchor themselves to a starting point when the parameters aren’t clearly defined. And the party that moves first is the one that sets the anchor.
You can use this technique when negotiating a salary, selling a car, and even settling on the terms of a work project.