Quote from ghettotrade:
Is it possible if I put 20,000 order for 3 dollars if someone makes a mistake super market orders even if I am 3rd to last I can get stocks cheap right?
or is something setup that blocks me from getting 20000 of SPY for 3 dollars no matter what?
realistically this could only happen in an illiquid market. I had shares of a sub-penny stock than I foolishly sold with a market order and got filled at 1/10th the price of the current bid/ask and took a 90% loss on the trade. But as JJacks said, if you tried this on SPY or any other major exchange the thousands of orders above 3 bucks have to get filled first.