You're not limited to taking the prices that are already up in the market. If you're not happy with the
current market prices then you can also enter an order to buy or sell at your own price and wait for another
trader to match that order on your terms.

You can set your own price to move to the front of the price line. If your price to buy shares is higher
than that if any of the other open buy orders waiting to be matched then sellers will see your order first. If you're selling shares and you set a price lower than any of the other open sell orders waiting to be matched then buyers will see your order first.

You can also set your price for further down the price line and wait for the market to move in your
direction. For example, if you wanted to buy shares but think they're a little overpriced you could set
your price lower than the current highest market price. The market may not move in your direction
and your order may not get matched, but you also won't buy shares at a price you consider too high.