Not sure exactly what folder you mean, but I literally have a 75 MB zip file (or rather, it's a .7z file, zipping would make it slightly larger). Unzipped its 700 MB though.
In that folder, bin includes files for compiling from x86/x64 to x86/x64, and in practice you only need one of the subfolders (in my case the x64 to x64 toolchain). The lib folder also includes binaries for x86 and onecore. If you remove all of those 7zip compresses the rest down to 25 MB.
You're kidding right? Hostx64\x64 is like 51MB, lib\x64 is 428MB, together they compress to like 116MB. And then you forgot the ATLMFC x64 files which are 465MB and bring it to 230MB compressed.
On the fresh install of the 2019 build tools lib\x64 is 200 MB. I tried using 7zip to compress to .zip instead of to .7z, that took the archive from 25MB to 75MB. I might not have enabled ATLMFC in the installer though, I didn't change the default checkboxes.
Edit: I feel like this whole discussion highlights the issues with the vs installer though. If it wouldn't create hundreds of folders all over the place it would be much easier to have a sane discussion about it.
