The first two sundering modules were. Does this mean that they weren't selling enough for this one to be worth actually printing?
I felt strongly that the price I paid for the printed "Murder in Baldur's gate" was too high for what I got. The price for this 'pdf only' offering is much more palatable, as long as the content is equal to or greater than "Murder". Hopefully that is why they did it.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.