It works both ways. If stock currently has 10m shares in circulation, selling 1,000,000 shares you expect to get significantly lower price per share, unless you

It works both ways. If stock currently has 10m shares in circulation, selling 1,000,000 shares you expect to get significantly lower price per share, unless you do it very slowly on a backdrop of high demand for shares. On the other hand, if you want to buy a million shares you can expect to pay significantly higher price compared to buying one share for exactly same reason - price depends on supply vs demand. In one case of selling shares you are inflating supply and thus dropping price, and when you are buying shares you are inflating demand thus raising the price.