[jedberg]

Yes, mathematically in a perfect spherical cow world, you are correct.

But I live in the real world. And in the real world, you can't switch jobs instantaneously back and forth, like you can trade stocks. In the real world there may not be a job available at the market rate. In the real world it takes months to find a new job even if there is one, and then it's even harder to actually get market rate.

So in the real world it make more sense to discount stock compensation compared to cash compensation to account for all of these things and the risk you take on by accepting stock based compensation.