

Storage and bandwidth definitely weren’t cheap in 2003. Additionally Steam provides features that a brick and mortar store could never even think of providing, including updates, DRM, instant access to global consumers, community features, in-depth data analytics, and the ability to adjust pricing in real time.
While a lot of the work Valve has put in Steam seems both obvious and ubiquitous today, these were features they pioneered for both developers and consumers.
I’d also like to point out that the only digital marketplace I’m aware of that charges less than 30% by default (Epic) is famous for losing billions of dollars in the endeavor.
Have you ever tried to setup a development environment in Windows? Windows fucking sucks for development unless you’re committed to handing over wads of cash for a VS license, and even then it’s really only good if your okay using a bunch of proprietary MS stuff.