Amazing amount of money locked up in coin collecting, and it's not even precious metal either.
The "50 State" series of quarters (25-cent coins) was launched in the U.S. in 1999. The U.S. government planned on a large number of people collecting each new quarter as it rolled out of the U.S. Mint, thus taking the pieces out of circulation. Approximately 147 million people are collecting the coins. Each set of 50 quarters is worth $12.50. Since it costs the Mint about five cents for each 25-cent piece it produces, the government made a profit whenever someone "bought" a coin and chose not to spend it. The U.S. Treasury estimates that it has earned about US$6.3 billion in seigniorage from the quarters over the course of the entire program.
In some cases, national mints report the amount of seigniorage provided to their respective governments; for example, the Royal Canadian Mint reported that in 2006 it generated $C93 million in seigniorage for the Government of Canada. The US government, the largest beneficiary of seignorage, earned approximately $25 billion annually as of 2000.