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.
Gerardo Parra, a lefthand batter, steps in to lead off. Harvey's first pitch on the way, it's a fastball on the inside corner for a called strike, nothing and one, a 93-mile per hour fastball to Gerardo Parra. Parra batting at .281 with 6 homers, 28 runs batted in. - Howie Rose's call of Matt Harvey's very first pitch in the big leagues... Mets at Arizona, July 26, 2012