Reducing file sizes with mogrify

Using a Mac 2.66 Quad running OS10.6.2, I'm creating files with mogrify:
mogrify -quality 25% -type optimize -format jpg ...image.psd

But the file sizes will not go below 33kb, irrespective of how low I make
the quality. Using Photoshop I can produce the equivalent quality image at
under 2kb.

Any advice on how to reduce the file size would be appreciated?

Regards
David McMillan