how come his +200-300 ped CLD order has been filled while there are plenty of fair MU orders usually?
That's another "quirk" of the Auction System. You buy and sell as a whole. As one single stack.
The system cannot and will not split it up separately to fill all the better offers first.
Therefore, "Quantity" has a greater priority than "Price". As it has to be sold as a single stack, whoever's order has the ability to eat up the entire stack gets it.
If there's two orders, both with enough "Quantity" to buy out the stack, the order with the "better Price" gets it.
However, it will still be at the price of whatever the "seller of the stack" has priced it at though.....since its fundamentally still a "buy-out" style auction.
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If the above is too hard to understand, then see it this way,
- whoever has the most amount of free PEDs in the order;
- that hasn't yet been locked up within other bids;
- that still has the ability to buyout the stack;
- that has the highest price out of all the orders placed, gets it.