That's fair, but I think losing perspective of the tradeoffs. The AMP preload will fetch only the main html file and AMP javascript. Images, videos, etc are all

That's fair, but I think losing perspective of the tradeoffs. The AMP preload will fetch only the main html file and AMP javascript. Images, videos, etc are all deferred until later. The javascript is cached for a year, so you probably already have it. So, compressed, this is probably ~100kb or less. Google doesn't start preloading 50 documents, it loads the top result or 2. Even viewing a hundred amp pages in a month is going to cost you less data than one 10kx10k unoptimized image that a publisher decides to load, which happens a lot. Note that AMP optimizes images too taking into account your device resolution, so it's most likely saving you bytes.