I don't know about average (and I don't feel like calculating it), but I have quite a number of pz3 files in the 30-40MB range, my largest is 56MB. The 30-40's are scenes with 2-3 (clothed) characters and a variety of props--your basic "room with people in it" kind of thing. So, I'd say that will be a very common range for me, with the note that Michael 2 will surely result in larger file sizes.