I've not learned Rust yet, but unless it does behave really weird, I can't believe that Electron and Qt have roughly same RAM usage. In my experience Electron has usually 2 to 3 times higher RAM requirements than Qt application of similar scope.
Did you come to this conclusion by taking measurements using real apps? Because if this is just your gut feeling, that doesn't make sense. The base memory footprint of something like Electron (just a simple Hello World app) is likely already heavier than a complete Rust-only GUI app.
For a GUI app, business logic is usually not where your RAM budget goes.
Not sure where you're getting your numbers, but as a quick test I cloned an Electron Hello World app[0], bumped its Electron dependency to the latest version on npm, and ran it. It came in at around 90MB resident on the main process, with a GPU process of about 70MB, a "zygote" process of around 60MB, and a separate nodejs process around 35MB. Even if some memory was shared between those, that's still quite a bit more than 40MB.
