My betfair commission was heavily discounted back in the day, but that was only on volumes of ~£50,000 a day, and a fair bit more on weekends. Nevertheless their commissions were outrageously high, but the scale of the liquidity they had available was amazing.
50k a day, was that money you were betting? Or were you managing a betting service and betfair was the underlying exchange? I know very little about that world
