> But it consumes at least 10x-100x more resources to run a web app than to run a comparable desktop app (written in a sufficiently low level language)
Does it? Have you compared a web app written in a sufficiently low level language with a desktop app?
I believe Firefox use separate processes per tab and most of them are over 100MB per page. And that's understandable when you know that each page is the equivalent of a game engine with it's own attached editor.
A desktop app may consume more, but it's heavily focused on one thing, so a photo editor don't need to bring in a whole sound subsystem and a live programming system.
Yes. I can run entire 3D games.... ten times in the memory footprint of your average browser. Even fairly decent-looking ones, not your Doom or Quake!
And if we're talking about simple GUI apps, you can run them in 10 megabytes or maybe even less. It's cheating a bit as the OS libraries are already loaded - but they're loaded anyway if you use the browser too, so it's not like you can shave off of that.