Someone explain this to me. Everyone says IB is cheaper. I can see in certain cases they are, but mostly not in others if you trade size. The bundled commission structure is $0.005/share. If you trade less than 2000 shares that is $10/side. Thats fine and inline with say Ameritrade's $9.99/trade with unlimited size. But when you get over 2000 shares, commissions get bigger: 1,000 shares = $5 2,000 shares = $10 5,000 shares = $25 10,000 shares = $50 25,000 shares = $125 50,000 shares = $250 I do lots of limit orders mostly 5000-10000 shares and I do get filled on active, high volume issues. What benefits are there to using IB in terms of commissions if you trade over 2000 share lots?