Ann: Block 9 Alameda 3 Appraisal Update (Alameda reservoir), page-856

The brokers pay volume fee's to the ASX/Chi x and its not per individual trade they then have different charging models to their retail customers etc which is averaged out across all customers etc

If you were a high net worth client that needed to say 2 million dollars worth of stock you'd go to your broker and ask them to sell. They wouldn't do this all in one hit as there isn't enough liquidity so their bot's and algo's come into play selling tiny bits at a time which could be over a few days etc. Note that this high net worth client would be paying quite a bit in brokerage fee's to do this so its not cheap for them either