Lighter webp is a lot slower than png

I've tried to use webp format to make loading big images faster, but it seems that webp is a lot slower than the same file in png when accessed from the _ipx path (or if accessed with NuxtImg):

http://localhost:3000/ipx//fractal.png produces a ~60ms wait:

http://localhost:3000/ipx//fractal.webp produces a ~400ms wait:

format="webp" also doesn't do better... http://localhost:3000/_ipx/f_webp/fractal.png produces a ~400ms wait:

It is even cached, and most of the time it's just connecting.

If i request a raw file from http://localhost:3000/fractal.webp it gives the cached file in no time:

Dev or production mode, nightly or stable, firefox or chrome doesn't matter, it's still a lot slower.

Repo to reproduce (it's really just a few files in the public directory): https://github.com/LasterAlex/nuxt_bad_webp

Am i doing something stupid? Is this expected? A lot of sources encourage the use of webp for optimization, so it's kind of confusing to see that the nuxt-image path is both slower than the raw public file AND slower than the less compressed file format.

Thank you for your time in advance.

Start with the linked nuxt_bad_webp reproduction repository and its public image files. Compare the _ipx and NuxtImg requests for PNG, WebP, and format="webp" in development and production modes, then determine whether the delay is expected or identify the image-processing path responsible; done means the behavior is explained or corrected.