I was going to say talk to bigtimespaghetti, but looks like he was already in on that thread. Also buying his book is useful to learning how to go about making coins.
https://bitcointalk.org/index.php?topic=1089977

But you'll have to pay for metals, the production costs, as well as the die for the coin to be struck with.

Edit: Here's an excerpt from Northwest Territorial Mint.

How much does it cost?
To create any coin or medallion, two engraved steel dies are required - one for the obverse or "heads" side and a second for the "tails" or reverse side. The designs on these dies are derived from hand-carved plaster sculpts created by experienced artisans. The cost for a single die typically ranges from $150 to $1,500, depending on the intricacy of the design. We also offer a wide range of stock designs at little or no charge. You should note that factors such as the materials used to mint your medallion, customized edges, engraving, high relief designs, specialty packaging, and other options will impact the total cost of your project.