I'm not experienced with dolls, but I have a friend who is a rare book dealer. He says that the prices online are often inflated, and that the highest prices are not to be trusted (in books, anyway). He is of the opinion that the general region of the lowest price you find online is probably a fair valuation, assuming a similar state of repair and condition. That is, if you see very good copies of a particular book (/doll?) on sale for $10, $12, $25, $50, $100, and $150, then a fair price is probably around $10-$20, and the higher prices are offered by people hoping for a na´ve buyer.
I should say, if it illuminates anything, that he is a serious believer in fair prices, and he usually prices books in his store at slightly lower than the lowest price he finds online.
I also agree with the people here that you should check with experts, which I am decidedly not.