For a Purnululu NP specific program the price on this offer is actually really good, especially considering it's fly in and out from Kununurra. APT (the operator) have the package brochured at $2,795 per person twin share, so $1,799 is a good deal. APT's lodge is also - in my opinion - the superior of the two main lodges in the park (East Kimberley Tours operate the other one).
As others have stated, it's probably not worth heading all the way over for this offering on its own - it's better tacked on to the end of a Kimberley coast cruise, or packaged up with a few nights in El Questro / Home Valley / Kununurra / Broome.