@NoImSpartacus it'll be some hedge fund's BOT and they don't pay typical retail brokerage rates like you or I do - they negotiate some kind of volume-based brokerage %, otherwise it just wouldn't be economic or make sense.
As for why they trade like they do, I've seen it across many many small and mid-caps, i think they do a lot of it for price discovery probing - at end of day they and their bretheren enjoy numerous advantages that "real" traders don't, including the ability to transact in .2 to .3c increments and therefore front run the true bid/offer, as well as pull orders in microseconds using their HFT IT setup installed right in at the ASX to allow milli-second order execution (before they get hit using micro-dummy orders up front) such that the bid/offer you and i are working off is a falsehood.
Such is the lop-sided playing field facilitated by the ASX and other exchanges with the full blessing of our pathetic regulators that OK this nonsense.
Gone are the days of "free and fair markets" and level-playing fields... we have to do the best we can despite this crap!
(20min delay)