By now, you know the basic arguments in the on-site versus off-site storage debate. External hard drives are fast (everything backed up in minutes!) and safe from hackers (you control the data), but are susceptible to theft, fire, and hard drive failure. Meanwhile, cloud solutions provide ongoing, reliable service, but are slower than on-site solutions, and (theoretically) more vulnerable to hackers.
But for today, let’s put aside the usual arguments and focus strictly on cost. Assuming your data will not be hacked, stolen, or burnt to a crisp in a house fire, which solution—cloud storage or an external hard drive—is more cost effective, byte for byte?