AssetSizeEstimation.cs

using System.IO;
using UnityEngine;
using UnityEditor;
using System.Text;
using UnityEditor.Experimental;

public class AssetSizeEstimation
{
    [MenuItem("AssetDatabase/PrintOutPathToFileSizes")]
    public static void PrintOutPathToFileSizes()
    {
        var allAssetPaths = AssetDatabase.GetAllAssetPaths();

        int index = 0;
        StringBuilder assetPathInfo = new StringBuilder();

        assetPathInfo.Append("Project Path,Library Path, Size (bytes), Extension");
        assetPathInfo.AppendLine();
        foreach (var assetPath in allAssetPaths)
        {
            //Don't update the progress bar too often
            if ((index % 10) == 0)
            {
                float progress = (float)index / (float)allAssetPaths.Length;
                EditorUtility.DisplayProgressBar("Gather path information", "Getting data", progress);
            }

            var guidString = AssetDatabase.AssetPathToGUID(assetPath);
            var hash = AssetDatabaseExperimental.GetArtifactHash(guidString);

            AssetDatabaseExperimental.GetArtifactPaths(hash, out var paths);

            foreach (var curVirtualPath in paths)
            {
                //The virtual path redirects somewhere, so we get the 
                //actual path on disk (or on the in memory database, accordingly)
                var libraryPath = Path.GetFullPath(curVirtualPath);
                var fileInfo = new FileInfo(libraryPath);

                //We have some additional files that we create that we want to ignore
                //They all have a size of 40
                if (fileInfo.Length == 40)
                    continue;

                var extension = (string.CompareOrdinal(fileInfo.Extension, libraryPath) == 0) ? "" : fileInfo.Extension;

                assetPathInfo.Append($"{assetPath},{libraryPath},{fileInfo.Length},{extension}");
                assetPathInfo.AppendLine();
            }

            ++index;
        }

        //Data is ready, output it to a CSV file
        var csvFilePath = "Assets/../FileSizes.csv";
        File.WriteAllText(csvFilePath, assetPathInfo.ToString());
        EditorUtility.ClearProgressBar();
        
        Debug.Log($"Data saved to: {Path.GetFullPath(csvFilePath)}");
    }
}