Offer your thoughts or opinion on the input financial query or topic using your financial background.

No transaction fee ETF trades - what's the catch?
AFAIK, It's also possible that the ETF company is paying Ameritrade for every trade you make. Even if your brokerage doesn't make you pay a fee to trade ETFs, the company that created and runs the ETF is still making money when you purchase and use their ETFs. See "What motivates each player?" at Yahoo Finance.