Butler: Not working or not complete $50 and under, complete and working $100 and under, with box, complete and great shape $150 and under.
Though shipping cost can reduce the value.
Skeleton: about $10-15 less then the Butler.
I would not consider either "rare", condition and desire more likely to create the sell price.
Remember if new and selling for $150, before Halloween, it sells for $75 the day after, while still new.
Now if it was the Doctor or one of the more rare (older) Gemmys, they seem (?) to sell up to the $300 price, above that are mostly asking prices.
Those asking prices, I assume is the wife asking "did you list that thing yet, we need the space", the husband having listed at $500, "oh yes its listed with lots of watchers". (please feel free to change wife/husband interchangeably)!!
just my opinion, the price is always what the market will bare or how quickly your want to sell.