I guess that's why we have €1 and €2 coins (1 EUR ≈ 1.18 USD).

People are quick to state this as if it's a slam dunk case for 'we shouldn't make them any more', but I don't understand the thinking there. An individual coin can be used many many times to facilitate many many transactions before it eventually falls out of circulation through loss or damage. The amount you should spend on making coins of a given denomination has nothing to do with what the total face value of those coins is, but needs to be traded off against the value to the economy of having those coins in circulation. If spending more money on producing higher quality coins enables them to remain in circulation twice as long, it might be worthwhile even if the cost exceeds the face value.

It's a different story if the material value of the metal in the coin exceeds its face value - at that point it makes sense to go to a bank, change money into pennies, then scrap them and sell the copper. That would be bad.

But the reason pennies are a bad deal isn't because of their manufacturing cost, it's because their handling costs exceed the value of incorporating them in a transaction. Should a store go to the trouble of keeping pennies available, counting them, storing them, transferring them to the bank? Or should they round up change to the nearest five cents and take a 4c hit on each transaction where you'd have been able to use pennies? If your average transaction value is over a hundred dollars or so, like most supermarkets, and you only handle cash on one sale in 50 say, if handling pennies in your cash-management operation takes more than a few thousandths of one percent of your budget, it's costing you too much.

Because that’s the entire appeal of the structure, the fact that it’s filled with a million dollars.