errrrr.... uhmmm.....
it may be either the app you save/compress in adding info in its own tag formats but unlikely that it would add 40-60k, or it could be that OSX adds 128 pixel big icon previews which guess what? add 40-60k to files pending icon detail. if you can upload from IE in classic at all that may work or try giving it a very low graphic icon yourself before uploading, like a 128x128 solid black square from photoshop. if its not the icon info or the app adding something i dont know what it is. if push comes to shove and you have a non mac ftp or email service, id email yourself the pic not stuffed or anything and the service it goes through should strip it of native resources making it a raw jpeg. good luck!