Problem is that I can balance the skill to hell and back as much as I want, and it works perfectly until your Enchant skill goes past around 70. That's when it takes off like a rocket and flies directly into cheese territory, no matter how much I gimp the charge per use GMST.
Take, for example, a 50-point fire on touch enchantment. My mod increases the base cost of fire damage to 6, so that's a 15-point enchantment. Now, let's assume that the cost per charge has been multiplied by a factor of ten. With an Enchant skill of 40, you'll need at least a Flame Atronach soul (105) to get a single casting out of it. Harsh? Yes, actually. But then you remember that enchant uses are instantaneous AND have a 0% failure rate, two advantages that an identical fire spell wouldn't have at a Destruction skill level of 40. For all intents and purposes, things are still balanced at this point.
But then take that same 50-point fire spell and stick a Golden Saint soul on it. At an Enchant skill of 40, you'll still fall just short of getting 4 consecutive uses out of it. Not too bad, given that we ARE talking about a tough soul to acquire. Once the Enchant skill hits 70, the number goes up to 6 uses. That's 300 points of damage near-instantly. It's damn nice, but worthy of having achieved such a high skill level. Still balanced.
Now set the Enchant skill to 100. Now you get 26 uses out of it. In a row. That's 1,300 points of damage spewing out of your enchanted codpiece of whatever literally as fast as you can mash the "use" button. I don't care what you think, feel, or say: THAT is cheap.
And try as I may, I just cannot figure out a way to clamp down on this aside from capping the maximum value of souls, which I REALLY don't want to do. I'm really hoping there's a GMST that addresses the exponentiality (I don't think that's really a word) of the Enchant skill, because I think it would function just perfectly if it were linear, instead. Or, hell, I'll just settle for setting a skill level of 100 to be functionally equivalent to a skill level of 60.
Any thoughts, guys?
(By the way, here's a quick chart of the casting costs for various enchant levels at various levels of the Enchant skill assuming that the cost per charge has been multiplied by a factor of ten: http://btb2.free.fr/temp/rawdata.txt)