They are generally valuble because they have been outlawed since 1860. However it depends on the age and condition of the coin and the current market value.
A Spanish doubloon in excellent condition with great eye appeal is a rarity in numismatics. They have been sold for well over $3,000. Value depends on conditon and rarity.
According to Northwest Territorial Mint, a doubloon is 7 grams (approximately 1/4 ounce) of gold. At 900/ounce, that is $225. melt value. A collector would pay more.
