If you take walk around the RoB marketplace ( 2 minutes east of RoB), you will notice a lot of ridiculously cheap stuff. For example, I've seen slices of Brodgar Blue for just 1 copper coin each, and Clothier's Thimbles for just 300 copper coins (those things take silver to make). It seems that people are mostly using their stalls to get rid of the stuff they don't need, which is why most of it is 2-3 times cheaper than the price you'd get in the IRC.
So, if you want coins and can't mint them yourself, you can buy them from me whenever you catch me in the IRC. It's a triple win: with coins you'll get more goods for your metal, vendor owners will get something for stuff they would otherwise throw away, and I will get a small amount of coins for my services. To be precise, I charge 9 coins per bar minted, or 1 coin per nugget. In addition to selling coins for bars of the same metal, I am also selling copper coins, which are by far the most widely accepted currency. For one bar of metal, you will get the following amount of coins:
tin - 60
bronze - 82
cast iron - 75
wrought iron - 300
steel - 900
silver (nugget) - 300
gold (nugget) - 400
Do note that my supply of copper coins is quite limited. Also, these exchanges ratios are based on my rough estimate of supply and demand, and are thus likely to change in the future as coin trade gives me a more accurate picture of supply and demand.