[exiguus]

I guess mostly picture. If you have 500 posts, one picture for each, and then optimize image for responsive and browser compatibility, there should be 3 to 12 images per image source set:

Mobile, Tablet, Desktop as breakpoints / AVIF with webp or jpeg fallback, Retina/Normal.

And this will increase the overall-size to 12 x 500 x 50kB = 300MB

[broken-kebab]

I doubt there's a practical reason for an average website, especially something blog-like to have pre-optimized pictures for that many screen types.