Answer #1: the bobbleheads are worth whatever you can get someone else to pay for them.
Answer #2: if you're looking for actual numbers, do a "Completed Listings" search on Ebay for them, and see what similar items have sold for. (Prices in green mean the item sold; prices in read mean it didn't.)
Fact: in the world of collectibles, anybody can ask any price they want. "Someone's asking $100 for it on Ebay" doesn't mean anything. "Somebody paid $100 for it on Ebay" is different because it means money actually changed hands.
I wonder what it’s like after death. Prob’ly it’s like it is b’fore birth. Is it nothing? Non-existence? That’s not hard t’understand, but it’s hard for people t’accept. It’s hard for them to imagine not existing because all of their memories are of their existence, not non-existence. An’ people ain’t too crazy about the idea of themselves not existing. - Harvey Pekar, “Short Weekend: A Story About the Cosmic and the Ordinary,” American Splendor #3, 1978.