It's currently the best idea I have for how to address your newly discovered phrase "Daddy, can you buy ________ for me?" Yes, I could probably buy you anything you ask for, but that's not the point. I want to teach you important life skills like understanding patience, merit, and gratitude.
The patience to wait to receive your reward or prize. The understanding that just because you want something doesn't mean you should have it and even if you feel like you deserve it, you may not get it. Finally, the understanding that you need to be grateful for what you have and appreciate that. What we give we can take away, just like the Lord.