mp3bu

Commissions fall , and costs depend more on bid-ask than on commissions or other explicit charge.

Bid - ask spread is really an information play. If the buy-side has superior information , the sell-side is at a disadvantage because they cannot tune the bid-ask in the absence of the information .

Simply put , the dealer does not know your urgency , and if you have superior knowledge of the stock , as a buyer you get the deal done at lower price to you , but higher price to the dealer than otherwise. Same for sale, you get a higher price , and the dealer does not get as low a price as they would like. Hence your cost advantage given your possession of exclusive knowledge is superior , putting you into an adversarial relationship