TD Ameritrade Holding CorporationAMTD

Despite the low switching costs, TD Ameritrade's clients have proved to be sticky. As such, competitors' offerings haven't really dented the transaction fees earned per trade, buoying profits.

Its asset-based revenue streams afford TD Ameritrade more stability than brokerages that rely more exclusively on transaction fees.

Its money market deposit account yields have been relatively impervious to interest rate fluctuations, giving them more of a revenue cushion than other brokerages that are more captive to the Fed's rates.

Due to its low variable costs, TD Ameritrade has been able to garner approximately 50% operating margins. Provided the firm can transition from one scalable business (discount brokerage trading) to another (investment advisory products), 41%-plus margins should still be obtainable through the downturn.

The acquisition of thinkorswim nets TD Ameritrade more active traders, who generally rack up transactional revenues during periods of high volatility. Read more 

A prolonged economic slowdown will likely spur more competition for fewer dollars in the online retail brokerage space. In that case, TD Ameritrade's pricing and volumes won't escape unscathed.

Most people who want an online trading platform have one. As such, new accounts will likely trickle in.

We doubt that its clients can stomach sustained periods of high volatility, which would likely result in lower volumes and lower revenues for TD Ameritrade. Read more