What if the project required you to use your hands – would you count that in the costs? I’m sure the cost on the black market for a pair of perfectly-mint newly-sawn-off hands is in the thousands of dollars.
I joke, but the point is that if you use something that is already in your possession and doesn’t get used up by using it, the cost is free. If you don’t have a smart phone obviously this doesn’t cost $10. If you do, then it does.
