For me it was over a megabyte, could not scroll smoothly, and had a broken header once I started scrolling.
PLEASE go browse a bunch of non-AMP media sites with adblocker off. 500kb is TINY by comparison to what is out there outside of AMP.
By the time you've loaded CNN's AMP page, you'll have loaded at least 4 MB: ~2 MB of AMP prefetching done on Google's search results page and another ~2.2 MB on the AMP page itself.
If Google adhered to its own page performance standards, as outlined here: https://developers.google.com/web/fundamentals/performance/w..., CNN's AMP page would be demoted in search results. However, since its AMP, it gets put front and center in search carousel.
Same goes for every single other AMP page.