Exactly. Stock owners are free to not sell their stock and this cannot be ignored.

I have a guitar that I could sell on the open market for ~$300.

But I don't want to sell it.

If someone offered me $300 for it, I'd say no. If they offered $400, I'd still say no. I'd say no at $900.

Why? Because I don't want to sell it and I don't have to.

There is some price that will change my mind, of course, but it has nothing to do with the actual value of the guitar.