Have you found any general rule of thumb at which monthly credit card transaction volume warrants suggesting to a customer that they have a third-party merchant review the charges to see if any savings can be had?
I don't want to blindly suggest people switch merchants unless there's truly a cost saving.
It would be easier if there was some rule of thumb such as ""at about $50,000 in monthly credit card revenue you probably are at the level you should have someone review those fees"".