Quote from DHOHHI:
No, you don't pay $7.50 per 1000 shares. You pay a penny on the first 500 shares and 1/2 cent thereafter. So the first 1000 is $7.50 and additional 1000 share increments are $5. I believe their commissions are the same as IB except for the first 500 shares. And SEC fees can be offset by MB paying interest on all cash and not excluding the first $10,000.
I was referring to a 1000 share lot since most people trade that size. A round trip will cost you $15 plus SEC fees. IB is cheaper - a flat .005 all inclusive for bundled and their unbundled rates are attractive too depending on your trading volume and style.
For a round trip at IB you pay $10.00 for 1,000 shares all inclusive.
Taking 2,000 shares as an example you pay $25.00 plus SEC fees on a round trip at MB whereas it would cost $20.00 including SEC fees at IB with their bundled rate.
Both places pay interest. I am not sure about the rates but I believe IB's rates are higher.