[antisthenes]

Yes, because the size of the average assets of a person relative to the size of the market is negligible.

This amount of assets cannot meaningfully move the market equilibrium, so the person will realistically sell all of it for 100% of what it's worth, with say a 2% margin of error.

The higher up you go in wealth, the less it is the case. But it's not black and white, just a scale.