Unfortunately, it looks like the 2 disc special edition is sold out.
I wonder if a publisher comes out ahead by offering a very limited special edition of a DVD issue. I guess you make more per unit this way (and perhaps assure the edition will sell out), but since you are limiting the special edition, the opportunity for extra income is limited as well. In addition, knowing there is a sold out special edition lurking out there, may dissuade some buyers from buying the regular edition in the hopes of grabbing the special one.
Since this seems to happen fairly often, I guess it must be profitable on balance otherwise publishers wouldn't do it.
I think from a profit standpoint the way to do it is the way the movie companies do it--just issue an "ultimate" edition every few years! :)