In my latest disclosure on IB they go over the fact they internally match Buy and Sell orders rather than place each out on an external exchange. IB rightly notes this eliminates exchange fees. What IB does NOT say is whether or not the sides to the trade see no exchange fees charged for the trade, or whether IB pockets the cash.
IF IB pockets the cash after using this rationale to get traders to agree to internal matching, this would be a fraud. Not accusing them, as I don’t trade Equities…