Same broker for buy and sell = XT - a cross trade does jump the...

Same broker for buy and sell = XT - a cross trade does jump the queue. It happens occasionally and can be of benefit most times.

"in that same instance all of sudden they manage to buy for you (jump the cue) only say 75 shares"

Your order is still "alive" for a month and you pay no extra brokerage unless you amend upwards and exceed the threshold of that particular brokerage rate. Then it is $10 to $25,000 and the % from then on - 0.12%...That is Commsec. What others offer, I do not know, but it will be somewhat similar, give or take a couple of dollars