onlyonemac said:

Current size of Apple's website (including obsolete software) = a.

Size of obsolete software = s.

Now let's suppose that Apple need to make their website bigger. Let's call the new size b.

The amount by which the website has grown in size, g, is b - a.

If Apple were to keep the obsolete software on the website, they would now need to purchase g units of extra storage (whether that be off-site hosting, cloud storage, or hard disks - it's irrelevant, they would still need to get extra storage).

If Apple instead took the obsolete software off of the website, they would only need to purchase g - s units of extra storage.

Clearly, no matter what their hosting arrangements are, they are saving money.

Click to expand...

You started trying to do math, but you didn't continue. The iOS App Store, for instance, has 1.4 million apps with more than 75 billion downloads. In October, 2012, the average size of an iOS app was 23 megs, according to ABI Research. 1.4 million * 23 megs is about 32 terabytes. This estimate is on the low side because the average size of apps has increased over time, but let's just go with the data we have.

Apple's legacy downloads is less than 8 gigabytes. This is about one fiftieth of one percent, or about 1/4000 of the size of the storage used for the App Store just for iOS apps. It's also accessed and downloaded significantly less than apps or current updates, so it probably never in the history of Apple even got cached in the CDN - it probably always lived as a static directory on one of Apple's servers.

It doesn't really matter - there's no cost in leaving files on a fileserver. Nobody runs a server at 100% of disk capacity, so the amount of storage ends up just being a rounding error. Buy a 2 TB drive for a modest server and it'll cost 40 cents one time for the amount of space that those downloads would take.

I'll post something when I buy an SSL certificate for mac68k.org and the files are available there for download