Except if we transact shares privately it doesn't show up in the market. If we offer to buy shares on the market we don't get to chose who we buy them from and

Except if we transact shares privately it doesn't show up in the market. If we offer to buy shares on the market we don't get to chose who we buy them from and we can't offer to overpay for a share, we randomly get shares from whoever offers them the cheapest. Clearly people manage to pump and dump but I suspect it's a little more complex/expensive/risky than two friends swapping shares...