I think "why is everything slow" is actually a really important question, but I'm not sure it's primarily lots of "this is cheap compared to X" decisions. A big driver here I think is layers of abstractions and inner platforms. I check my email in by browser now, I used to use mutt. Webmail on top of JS on top of browser on top of OS (with several of those systems having their own layers and places that add latency) is great from a perspective of checking email from anywhere but it's a lot slower than C on the OS directly.

I recently got into doing a lot of live music for dances on my mac, and I've ended up writing everything directly against CoreMIDI in C. Sure, it's would be more convenient to write in Python, but latency in music is even more painful than elsewhere.