Zerodha promoting to trade at RS 20, per trade and they do not charge brokerage as per the volume. SO this scheme will attract customers to trade with big quantity in single trade.
But if you want to check teh reality then open a trading account adn find how they are cheating.
I was trading at ICICI securities, Sharekhan, but when I saw the advertisement of discounted brokerage I got to know that this can save a lot of my brokerage.
But they charge more in Turn over charges, and they do not have clarity about the penny stock brokerage charge. And they will put a minimum brokerage amount on per unit instead of charging per trade.