That might be false economy. Most images in a page would come above 30kb. I've seen 3rd party widgets for chat and support sometimes bundle their own copy of the React framework, not to mention huge chunks of CSS, most of which are unused.
If you're putting jQuery in your main application bundle then it has to be parsed and executed before you can do anything. That's not the same as an equivalent sized image which just needs to be decoded and painted. If it's a chat widget hopefully you're loading it separately. I agree that CSS can also be a problem.
Pretty sure serverside rendered html works just fine before JavaScript is parsed and executed..