not knowing their particular formulas or they're basis, this is an exchange.
The basic idea of an exchange is you are betting that a stock will go up so you buy. But the exchange is matching you up with an order to sell that same stock.
Using your example, you ask the exchange for x shares at market price.....someone has a limit order to sell the shares at $10.35......the exchange matches you up to the guy selling his shares and takes 1% from each of you for their trouble.
How it works in the real world anyway. If you don't like the market pricing, do limit orders and you'll be within 1-2 cents of your asking price either way.