No, you can buy shares at more expensive prise.
1 Share = 1$ (selling price), and purchase price for the same share at the same time = $2 (for example).
10 players buys 10 shares for $2 each (20$)
Money supply: 20$ (100%)
So you mean that the sell price is the half of the current buy price? So the sell-price is the previous price of the buy-price?