File size will vary depending on scene complexity, size and quality of textures, and number of textures. A typical game-ready asset with two texture sets limited to 2k resolution will generally be around 10MB.

Untextured high poly models can be loaded as well. A scene with 1 million triangles and no textures will be around 22MB. If you’re uploading content to ArtStation (which has a limit of 15MB) you can try decimating your mesh in ZBrush or other 3D modeling packages to reduce file size.