What is a reasonable, average file size of images edited with layers in Photoshop?

Question

When I edit photographs in Photoshop, I have noticed that the final file sizes average between 300mb and 700mb. I try to use smart objects whenever possible, and my files tend to have quite a few layers. I am a bit confused as to why my original 5mb .NEF raw images grow to several hundred megs as I edit them. Is this normal for .psd/.tiff files after edits have been made?

Answer

This is how big my .psd files are:

I have a lot in the 300-700MB range (mostly around 300MB). Some of these would be larger (probably a couple of gigabytes) but I flatten the layers occasionally to stop the files getting too large.

Is it excessive? I don't think so, if you have plenty of layers. Quite a few of my bigger files are panoramas. One thing I have noticed it that if you turn off "compatibility mode" when saving the files can be quite a bit smaller.

Check more discussion of this question.