Well, the $50 (nominal value) coins were worth lots more than face value in recent times. It would be very interesting to see what the US government would do if people were paid in US eagles, and declared income in the face value of the US coinage given to them, paying the appropriate tax on the stated face value. Very interesting, indeed.
On second thought, the US government would probably say that the $50 nominal face value of the coin wasn’t the real value of the coin, and the receiver of same would owe income tax on $800 of ordinary income for every coin received (at least today) no rational needed - just pay us or else.