As others have said, the Pewter versions are quite cheap. You shouldn't pay more than a few dollars for any of them. Original Comita Americana (in bronze) start above $3,000. A bronze John Stewart (the only one not minted in Pewter) will set you back $50,000+ (assuming you could find one). 19th Century restrikes are much much cheaper (hundreds to thousands of dollars). Original silver examples run much, much more (a Washington example just went for $282,000). Likewise, 19th Century silver restrikes are much much cheaper ($5,000 - S20,000). While Gold examples do exist, they are virtually all in museums. If you are really interested, get a copy of John Adams' Comita Americana book
Are those the 3" medals? I believe the one the OP posted is one of the smaller, pewter medals. You could buy them individually or as a complete set for very little. Chris
Chris the medals are between 47mm to about 56mm not quite 3 inches. They are more like 2 inches to 2 1/2 inches.
The actual Comita Americana medal sizes vary: Geo. Washington ~69 mm Gates ~56 mm Wayne ~55 mm deFleury ~46 mm Lee ~45 mm Stewart ~46 mm Morgan ~56 mm Wm. Washington ~46 mm Howard ~46 mm Greene ~56 mm Jones ~56.5 mm