Hi HHushH….
The blend file, depending on how you are saving it can be very light, under 1MB or heavy in the 100’s of MB or larger. In most cases the size of the blend file is related to the textures sizes, not the actual model itself. Be sure to CleanUp your scene file and remove unnecessary geometery, materials, textures, etc. and of course be sure to compress it.
.Bin files are large and bloated which is why compression is needed. The .bin.xz files are typically half the size. If you are running your app in compressed mode…you don’t need the .bin files or the .gltf…just keep the .xz
Is it possible to have a 50MB .bin…oh ya…I have had some much larger…in those cases…you need to break up your scene or remesh it to get it lower depending on your target devices and browsers. Good luck.