The raw materials and production of bills and coins aren't free, of course. Here's what the US Mint and Bureau of Engraving & Printing spend to make our money:
$0.30: Sacagawea dollar coin
$0.11: $100 bill, quarter
$0.09: $50 bill, $20 bill
$0.08: $10 bill, $5 bill
$0.06: dime, nickel*
$0.05: $1 bill
1.5 cents: penny*
*these prices fluctuate slightly based on copper prices
So it seems like the government could save money by buying pennies instead of making them! I'll sell mine for the cheap price of 1.25 cents each. :)
Along those lines, did you know that all pennies made after 1983 are not primarily copper? They are actually 97.5% zinc with a copper coating. This is due to the rising cost of copper throughout the years.
You might be more trouble than you're worth, pennies!