carl wolf wrote:
"I mean, it's a screw, which most likely costs one half of one cent. don't sweat it. "
If he mucked up the screw head, why would Apple replace the screw free? If the screw threads are mucked up, perhaps he managed to damage the internal threads of the hard drive mounting assembly. Do you think Apple will replace that assembly free?
I've found that a lot of companies will help out with little things because it's a lot cheaper to replace something cheap like a screw rather than risk losing a future customer. I dropped my cell phone once, and it scrambled the display, likely due to a ribbon connector getting misaligned . When I sent it into Nokia, I wrote down exactly what happened, and expected to receive a bill. I got a new display and a note that it was repaired for free as a courtesy.
You seem to making a lot of assumptions. At the very least the OP can ask if it can be repaired. Maybe it's free, maybe it's not. However - this is not an expensive thing to do with the right equipment, and I would surmise that an Apple Store would do it either for free or for a nominal cost.