Well, https://jmail.world/jacebook-logo.png is 670KB by itself and loaded on initial load, so I think they might have blown your suggested traffic budget and still have some optimization to do.
Fair enough, I just loaded some pages and some of them are even bigger than 2MB. But then again those static resources would be cached client-side. So unless you have 450 million unique visitors who only ever go to one URL on your site, you are looking at significantly less per pageview. I reloaded the frontpage with caching enabled and it was ~ 30kB of data transfer.
How is that image 670 KB!? Definitely some optimization low-hanging fruit there.
Edit: dang, even pngcrush can't get it below 580 KB. Disappointing performance on PNG's part.