> while at the same time assuming that the company can purchase and sell all the shares at a set price For large cap companies that trade tens of millions of s

> while at the same time assuming that the company can purchase and sell all the shares at a set price For large cap companies that trade tens of millions of shares a day, you can figure out how much you can buy without moving the market. For less liquid stocks, you can also spread the buys out over a period of time to aim toward an average buy-in price. The phenomenon you describe is called slippage [1], and those entering and exiting large positions are aware of it. > it seems awkward to assume both that the volume purchased by the company significantly increases the price of the stock I'm not implying that the reason why the stock price goes up is because the company is buying shares. The purchase may be done based on quarterly/yearly projections showing X% growth can be expected in the stock price in the future. [1] https://en.wikipedia.org/wiki/Slippage_(finance) https://en.wikipedia.org/wiki/Slippage_(finance)