So if i am in a restaurant and i order i pasta bolognese,.. i get pasta cheese and i am complaining you say, if you don`t like it go eat somewhere else!
WTF CEX.IO
Well, actually we explained the nature of the error and the user will be refunded within the timeframe mentioned in our terms of service.
You also stated that you cannot identify all affected users, so many will not get refunds and you will profit.
$0.005 multiplied by half of your userbase, lets say 200000, will amount to $1000, a small but not an insignificant amount that would not be yours to keep legally.
You claim "due diligence", now prove it by doing what you should do, identify every single user. Otherwise you are acting like those car manufacturers that don't recall dangerous vehicles and would rather pay off a few people to keep it all quiet, because its cheaper.