WoWI doubles my image file size?

[Phanx]

For some reason WoWI is more than doubling the file size of the image I'm uploading for my project. On my local machine, the image's file size is 207 KB. Uploaded to Curse, the image's file size is 207 KB. Uploaded to WoWI, the image's file size is 508 KB.

Compare:
• http://s.wowinterface.com/preview/pvw35256.jpg (508 KB)
• http://static.curseforge.net/content...ured-aggro.jpg (207 KB)

I don't see any visible difference in the image, so I'm a bit confused as to what WoWI is doing with the file that causes such a massive jump in the file size.

Edit: I uploaded another version of the same image with smaller dimensions, and see similar results:
• http://s.wowinterface.com/preview/pvw35257.jpg (272 KB)
• http://static.curseforge.net/content...ed-aggro-h.jpg (112 KB)

And with an older image on another project, the file size is almost tripled:
• http://s.wowinterface.com/preview/pvw26154.jpg (153 KB)
• http://static.curseforge.net/content...dsup-group.jpg (57 KB)

Whatever the problem is, you'd probably save a nice chunk of bandwidth by fixing it.