Go to online auctions and search for it...that should give you the best proce guide....as for what I would pay for it....not much...I don't collect many coins after 1964 and I'm one that also doesn't think there is such a thing as PF70 or MS70....there will always be something on a coin. Speedy
PCGS lists it as $225, but I think that is generous considering PCGS has graded 57 of them making it is only a R5 (and including those graded at NGC and those not yet graded, it is likely that it is an R4). As such I figure it should be worth about $75 or so. Now to answer your question, I personally wouldn't pay more than about $15 for it. P.S. Are we talking about this auction?