Well, there's a multiplier between the nominal capacity and the capacity you actually need to purchase for your whole system. You're not buying just that 1 TB. You probably want at least two live failover servers at least, maybe more. Plus however many layers of backups and disaster recovery; a year of weekly backups makes your 1 TB into 50, even if it's offline storage.

My own company struggles with that - throwing more storage on the live db is easy, so we've kept doing that for years, but pushing around multi-terabyte backups is getting cumbersome and we're going to have to slim down the data in prod even at the cost of engineer effort.