Part of the reason for the Italian guns being valued more may have to do with the proofing. Italy alongwith 14 others (Austria Belgium, Chile, Czech Republic, Finland, France, Germany, Hungary, Italy, Russia, Slovakia and Spain, UAE, UK) is member of the "Permanent International Commission for Firearms Testing" (CIP). American arms are NOT 'proofed' by any national oversight body.
The standard proof of pistol, revolver and rimfire weapons is performed with overloaded cartridges that produce 30% more chamber pressure than the CIP maximum pressure limit for the same cartridge in its commercial version.
So maybe that is considered as some kind of special endorsement. Otherwise the American and Italian guns are the same, practically.