webk transferred 627 Kb, and is fully functional. Slack, Discord, Teams, and friends could all stand to trim their web application's bloat a bit and take a lesson from this.
The competitive angle is really delivering a fast/snappy/responsive experience on mobile or desktop. That in itself isn't going to save you, but it is an advantage if part of the sell is a high quality experience.
Re:interesting, for instance I just started experimenting with inlining all css/js into index.html (so far the js part is problematic), minifying classnames, and I'm curious if it'd be possible to even minify js module names etc.