I would not call them rare but outside of a few "special" runs like the Jabo Lawnchair types, there are not a huge number of metallics out there but still they are not really valuable. Nice ones with the underlying marble also being nice can be $5 on up. Obviously a Peltier Peerless Patch with metallic would be worth more than one like you showed. Again, as with all marbles, condition is paramount.