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.