US coins are backed by the might and presence of the US government. The US Mint produces all the coins and distributes them through regulated channels, and at high security.
In the UK, according to the Royal Mint: ”
The cost of producing United Kingdom coins varies according to the specification of each denomination. The value of metal in each coin accounts for a large part of the total cost, but it is also necessary to take into consideration the broader costs of the manufacturing process. These vary according to the complexity of the coin. The Royal Mint does not reveal exactly how much it costs to make specific coins as such information could be used to its competitors’ advantage.”
While there is speculation that mints worldwide have similar issues to the US, I will focus on US coins. It is generally acknowledged that the mint spends more on manufacturing pennies and nickels than than they are worth.
The coins (and notes) are minted to be as unique and resistant to copying as possible. As such, many of our minted coins are made of valuable metals vs. cheap alloys. sometimes these metals exceed the value of the coins. Even “cheap” metals, like zinc (used as a filler to reduce the copper content in a penny) have increased in cost over time.
Production is in the US, by Federal employees, paid on government pay grade. Private companies and other governments may be able to produce cheaper coins, but these are not backed fully by the US Government…