Couple of instances that point to the unexplained & inexplicable importance of the doll sans as the conduit.
First, at the beginning, when John gives the doll as a gift to Mia, when she exclaims something on the lines of "I've been looking for this for so long. Where did you find it?" "Well, I have my means"
Secondly, at the end, when an old women exclaims to a shop owner about the doll, saying that she wants to gift it to her daughter who is a nurse. The shop owner replies with something like "Oh sure, that doll is a collector's item"
Even before being turned into a conduit, the doll was hideous & scary. Why was it treasured so much in the movie(as a doll, not as a conduit by the cult)?