I could use the $10 on something worthwhile rather than stuff worthless-to-me accessories in my drawer.
...since Apple wants $20 for a spare charger and $20 for a spare cable, you could probably offload them onto someone for $10. Then, its useful to have more than one charger, and some of my older ones are too low power for new devices. Or maybe you want to re-sell your old phone along with its original accessories...
Anyway, I wasn't pooh-poohing your idea in principle - I just think that you'd be lucky to see even a $10 price cut.