Q: Exporting an ePub from pages on a retina MacBook Pro the size is 10x that of the same export on a MacBook Air. Why?

I am exporting an ePub from a 57.6 MB pages file on my retina MacBook pro and the exported epub is 982.9 MB in size. Exporting the exact same file from Pages on my MacBook Air give me a 97.8 MB ePub file.

Both machines run OSX 10.8.4 and Pages 4.3. And the Pages file resides in my Dropbox.

What is going on here?