Topher Chris, each hiker needs a permit, sorry. But seriously, the unused permits are pretty easy to get.
Ntintle: Buying, selling, exchanging is practically impossible, but picking up unused ones is they way to go. Reality is that very few hikers visit this site, so even though the information is here, lots of people don't know about the walk-in system. Here's a thread to start reading: Permit needed for June 3rd
In it, find the link to the Unused Whitney Permits. Checking there, I see that last year, there was never a full-quota day until June 30, for both overnight and day hikes.