I have a familial requirement to answer as my relatives, Mr and Mrs Johl wrote books on stamps (him) and dolls (her). So my answer is I have no clue. Since normal is going for $5, inverted is worth at least $10 if for no other reason than as a stamp office conversation piece. Heck in the correct mood, I could see spending $20. (Yes! I own bears.)
Be aware you are talking to philatelists (stamp collectors) here and I suggest you Google, "Doll Forum" to find an active doll board for their take on your question.
Otherwise the best I can do is offer what normal look like:
Okay, someone else can grin and bear an answer. Come on, do it.
Edit: added doll forum suggestion.