I had an iDrive account with over 10 Terabytes for one year. 1st year was less than 10 $ for testing, but when I accidentally came over quota for only some weeks they charged me more than 400 $. They say: "Quota overages are charged at the rate of USD 0.25 per GigaByte per month for as long as you are over quota."
So please make sure to never overrun your quota! Or even better just don't use services where scam is part of business-model.
There were messages from iDrive coming in by mail, but no question or even better an automated sync stop before confirmation. Unfortunately these mails were automatic sorted so that I didn't get them in time.
I guess it's part of their business model where they earn quite a lot of money even they lost me as customer. It was similar in Europe with mobile plans, where they charged you whatever they wanted until it was capped to a max of 60 €/month.
At least I learned out of that, that I have to be more careful with some things.