What is the most valuable gold coin ever minted?

Could you please elaborate on what constitutes the most valuable gold coin ever minted? Is it determined by its rarity, historical significance, or perhaps the purity of the gold used in its creation? Are there any specific coins that stand out as exceptional examples of this category, and if so, what are their unique features and why do they hold such a high value in the world of numismatics and cryptocurrency enthusiasts alike?