As further service, the government protects the value of the money through counterfeit laws. There is only one authority that can print money and stamps. But, the government does not, by law, guarantee a specific right to trade the property of a dollar with another property. While there are arguable exceptions. Think about communism.
Price regulation tends to correlate with distortions of property ownership.
Property law on symbols are effective when the law has consensus. The question of where to draw the line is a human question, and humans must find comfort in the answers. If the answer gives the appearance of unduly constraining freedom or, alternatively, violating an ethical reserve, the line drawn will not be obeyed. The laws governing money and stamps are wonderful examples of laws that invigorate and incentivize free commerce, minimize government, and pay their own way. Stamps in Cyberspace Symbols in cyberspace can be similarly protected.