Box of armor

So basically I am not sure if many people know about this, but you can create full sets of armor for one slot. This is a mystic forge recipe and you can make a lot of gold off these things. But I have a question for anyone who already knows about this. How do I know how many mystic coins to put in the mystic forge to create a certain type of armor set recipe. I cant seem to figure it out.

http://wiki.guildwars2.com/wiki/Myst...atchel_Recipes

5 Bottle of Elonian Wine
20 Crystal
50 Mystic Coin
1 Crafted Chest Armor


^ Just an example, materials change depending on the item quality (Uncommon, rare, exotic, etc)