They are not altering anything. The MMs are required by FINRA/SEC rules to execute the order at the lowest/best price possible at the time the order comes in. If you had a small order, would easily be filled by an MM, not to mention if they executed every order at the price entered and only that price, manipulation would be rampant and the ability to chart and develop metrics for tracking securities would be destroyed.
News 
Market Data 
Discover 
AI
