On the XpMailingList, JohnBrewer described a toy store analogy he uses for the PlanningGame:
Feature negotiation without the planning game is like a kid in a toy store:
Kid: I want the scooter! And the Star Wars Play Set! And Kingdom Hearts! Parent: I don't think I can get you all that. Kid: But I waaaaaant it! You'd get it for me if you loved me!
Feature negotiation with the planning game is like a kid in a toy store with an allowance.
Kid: I want the scooter! And the Star Wars Play Set! And Kingdom Hearts! Parent:
Well, you have $60, so figuring in tax, you can get about $50 worth. The scooter is $20 and the Star Wars Play Set is $30. But Kingdom Hearts is $50. Is Kingdom Hearts worth as much to you as the scooter and the play set?
Kid: Hmmm.... Can I have any more money? Parent: No. Kid (possibly much later): Ok, the scooter and the play set.