What'so frickin special about Mac Memory modules?

A guy at work is looking for:

Apple Memory Module: 4GB 667MHz DDR2 FB DIMM ECC (2 x 2GB)

At the Mac store, that's $999.00

That cannot be right.

Not when I can get apparently the same thing here for $76.54

Now, I'm not a Mac guy, so am I totally missing something?