http://forum.square-enix.com/ffxiv/t...236#post359236

Most material synthing have both a 1-set recipe and 3-set recipe. Some, like Ore => Ingot, have a special "discount" probably due to synthesis ingredient box capacity. (3 ores = 1 ingot, but 8 ores = 3 ingots)

However, I don't know about Alchemy, but as far as I've looked, there's no similar recipe for Alchemy material.