How much is a 1973 newspaper clipping 'Frazier and Foreman fight' is worth?

One sure way to find out what something is worth is test the price that the market will bear, i.e. put it on Ebay. Assuming Ebay is (more or less) a fair marketplace at the time at which you sell the item then the marketplace can give you an idea of what the item is worth.

Pricing an item this way also "automatically" takes into account the condition of the item and (because of the size and scope of Ebay) also takes into account the rarity of the item. Where such a method fails is in the assumption: if the marketplace isn't fair (your item doesn't have the proper exposure or the people who are interested in your item aren't looking on Ebay) then you will of course fail to realize its true value.

But I still think Ebay will give you a good 1st-order approximation.

While a newspaper