Jack: "But I really really REALLY want a lego Batman!"
Me: "I know. But it's $25.00 for a two-inch high Batman. I just can't spend that much on something like that right now. Maybe you can save up your allowance."
"And if you do save up $25.00, you might even decide you want something else even more, you know? Something that's maybe better than a two-inch high Batman. Maybe the Batman won't be so important to you anymore."
"Hey, look! This has been important to me from yesterday to today!"