Also noticed the first page of gmail uses 0.5Mb to 1Mb of data transfer just to load a single screen sized page of simple text.
That's because Google increasingly send great globs of Javascript to your browser because they want your computer to do the work of rendering the user interface rather than making their servers do the work in server-side rendering.
Look at the homepage for google dot com.... see how much Javascript crud they're shovelling your way.