If you deposit $10,000 you will receive 12,000 miles over the course of a year. Let's say those miles cost BankDirect $180 ($0.015 each). That's much less than other banks are paying to attract and hold checking accounts (see earlier messages in this thread).
Right, but at $250,000, the numbers are pretty different. That's $3750 over the course of a year. And if it weren't for FDIC limits, many would go even higher.
All good promo and teaser rates seem to cap out at $25K. There's a reason for that.