The price should be comparable to the 1933 Saint Gaudens double Eagle, which last sold for $7,590,020. I note that gold coins generally sell for more than nickel coins and large coins are worth more than small coins. This fact alone might explain the discrepancy in the price. If we examine the mintages, a mere five 1913 liberty head nickels were struck compared to 445,500 1933 double eagles.
All five liberty head nickels are currently accounted for. Two are in museums, leaving only three available for private collectors. Most of the 1933 double eagles were melted, but some escaped. The US government's position is that there is only one 1933 double eagle that is legal to own - a specimen legally exported by King Farouk. The secret service has been actively seizing 1933 double eagles, stating that they were released illegally. The same argument could apply to the 1913 liberty head nickels, which were made surreptitiously at the Philadelphia mint.
In 2004, the government seized ten 1933 double eagles from s Philadelphia jeweler who submitted them to the government for authentication. (read that story here) This means that there are at least 11 1933 double eagles that are accounted for. There are undoubtedly more that are secretly owned. The 1913 liberty head nickel, is therefore the much scarcer of the two coins. In the future, the government could release some of its 1933 double eagles, which would cause their values to plummet. There is no such risk with the 1913 liberty head nickel.
A good story is an essential ingredient to the value of a coin. Both the 1933 double eagle and the 1913 Liberty Head nickel have stories -- but I find the nickel story more intriguing. It began with someone clandestinely striking the nickels at the Philadelphia mint. Then,as a rouse, a mint employee placed ads offering to buy any such nickels (which were not thought to exist). Years later, five nickels magically appeared. One of the nickels was purchased by George Walton, who was killed in a car accident on the way to a coin show. His heirs recovered the nickel, but it was thought to be a fake -- only to be discovered as real years later.
A great story, and a great nickel -- clearly worthy of a seven million dollar price tag.
Read more about it in the book Million Dollar Nickels: Mysteries of the 1913 Liberty Head Nickels Revealed... or visit my webpage at peterplanchet.com.