Furrek Manually removing "invalid prices" isn't a solution though. Anything that requires manual intervention is bad.
It would be better to give users the ability to filter out lowest prices that have only been available for a day (or even give users the option to choose the time period).
Failure to make this option makes the alert for Historical Low values worthless, because users who are waiting for a historical low price are unlikely to be in a position to react to something that lasts less than 24 hours (I'd personally argues a minimum of 48 hours).