Here in California we have vending machines that will fill up your container with drinking water. Imagine one of those machines from a fictitious supplier, SeaGreat, that would fill up a 5 gallon bottle for one dollar. Imagine this machine is outside of a convenience store that is always open and which sells sealed 5 gallon bottles of SeaGreat water. The question is, how much do the full complete bottles of SeaGreat water cost? Obviously, they must be more than one dollar. Obviously. Imagine going inside the store to see how much money you were saving by bringing your own bottle.

What if it was not more than a dollar? What if the full bottle was $.75?

If that were the case you would have to reconsider one of the most fundamental ideas of economics, that one plus one is greater than one. Well, start reconsidering! Because in the crazy world of computer hard drives, this is exactly the situation. It turns out that at this time it is clearly less expensive to buy an external hard drive than the equivalent internal model.

Here are some examples.



The bigger the drive, the worse it gets.


This shows an extremely rare (perhaps discontinued) internal model but that was as cheap as I could find. I just liked how these came up together on the same search result. Looking at results for "8TB internal" the only drives with more than 1000 reviews were $274, $325, and $307. Also several people in the reviews for the external drive report that it does contain a 7200 RPM drive, so forget the tempting idea that the performance specs must somehow be different.

Just to make sure you’re clear about what’s going on, here is a $23 box that allows you to convert an internal drive into an external one.


You would think that an external drive would cost as much as the sum of this box and an internal drive. But no!

It’s not just I who have noticed this. There’s even a special term for the process of extracting an internal drive from an external enclosure. Searching for the word shucking turns up all kinds of confirmation of this weird situation.

Here’s a good recent article about it. But it’s not even a recent thing. I’ve been sensing some confusion about this for years and it seems that is accurate. This discusion from 2013 is simply titled "Why are External HDDs cheaper than Internal HDDs". No good answers are proffered. And same story in 2015. Here’s another asking the question; no proper answers are even attempted and comments are skeptical that the situation can be possible.

Knowledge is power and my purpose is to alert people to the fact that something very strange is happening in this market. If, like me, you sometimes buy stacks of large internal drives it can be worth exploring options that would seem ridiculous. That said, careful research may be required. Some people believe that recent integrated USB controller boards will make external drives incompatible with SATA controllers.

Hopefully some clever people are using this as an arbitrage opportunity and breaking apart external drives and selling the parts. Just be aware the next time you’re shopping for hard drives and something seems crazy—it’s not you.