Marty, I really agree. I have suggested to Inyo that they offer partial refunds -- one could even do a graduated refund (the earlier, the higher the amount). But I was told that it was a really big deal and a big problem to give back money. (I sure don't understand, since every commercial sales web site gives refunds.)
Countering what SB wrote, if they would give a partial refund, they could then re-sell the slot, thereby making MORE money. Right now, those unused no-show slots are given away free to those who walk-in.
Adding to SB's recommendation: Check the numbers in the Unused Permits
pages, you can see that for practically any mid-week date during the summer, you can always get a free walk-in permit. Book a flight! You are sure to spend more than a day or two, given the expense and time required to travel here. So if you plan on showing up and trying for an unused permit, you will probably get one. But if you don't, you can head up several places and day hike, then come back the next day. I've only seen a few reports where people didn't get an extra permit when they tried for one.
There is so much to do and see here, that you should plan a trip. You will not be disappointed.