That doesn't even seem so unreasonable. Is that the limit though? My cable puts a gigabyte a second down it so I wouldn't imagine that would hit the limit.
See the section "Resolution and refresh frequency limits". The table there shows it'd be able to do 4k/144hz/10bpp just fine, but can't keep above 60hz for 8k.
Its an uncompressed video signal, and that takes a lot of bandwidth. Though there is a simple lossless compression mode.
It seems markdown formatting ruined your numbers because of the asterisks. Whatever is written between two of those turns italic, so they're not ideal for multiplication symbols here on Lemmy (or any other place that implements markdown formatting).
I think the maths got a bit funky there. I don't think a cable capable of such speeds would struggled to do 60Hz at 4K, it surely doesn't need close to a gigabyte a second?