How do stock photo stores like gettyimages.com and photos.com compress
their jpegs so much?

I am a graphic designer, and I have noticed that stock photos are
compressed to much smaller sizes than I can achieve, yet they lose no
quality.  I work with photoshop a lot of the time, and I "save-as"
jpegs a lot as well.  But when I have a 24 mb image, and save it at
the maximum jpeg level, the resulting jpeg is somewhere around 6.9 mb.
 But the same 24 mb image saved by gettyimages (for example) would
have a resulting file of around 1.3 mb.

My question is:  What compression software are they using?