It’s very arbitrary. Silver or palladium are more similar to gold than Bitcoin, but no one even tries to compare the er... “market caps” of the mined metals to each other.
It would be just as easy to say that Bitcoin had properties similar to Copper and try to back a valuation out of that. Either comparison borders on silly.
It's not arbitrary; gold (unlike copper) has been money for 5000 years.
And unlike copper, the United State's dollar was backed by gold for a majority of the 20th century while most other currencies were pegged to the dollar.
And finally, unlike copper, there’s $8-$10 trillion dollars worth of gold being used as a store of value globally.
Bitcoin has all of the core attributes of gold with the addition of being digital and having a fixed supply.
It would be just as easy to say that Bitcoin had properties similar to Copper and try to back a valuation out of that. Either comparison borders on silly.