I believe a coin's worth is primarily based on what you are willing to pay for it.

But, I personally think the ebay bids you mentioned are way too high. I would wait at least a couple of months to see if the prices stabilize and for more PF70's to get out onto the market.

Also, you may want to check out some of the auction sites, such as Teletrade or Heritage, to see what these coins are selling for.