Every exchange has it's own rules, some will will timestamp the order, some will prefer a trade at the best bid/ask (buyer pays the less for a seller to get the most),....
Many exchanges first fill the market orders, as these are more liquid.
If you really want to be in and willing to take some risks, you would prefer the market order.
Now, if you suspect a MM to mark up, cancel your order: you most probably will get the message "too late to cancel, order filled".
Works on most exchanges with specialists or MMs, these guys are greedy on the commission fees, mark-ups are there just for some extra fun. <g>
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