In a deck with eight enchantments on the battlefield, that's eight mana off a single creature
I ended up using the flavor text to reinforce that the Surgeon Commander liked "creative templating." The name came about because I realized that since this was a Commander-focused card and we were already going to make a joke about templating for Commander, we could pick a name that played into the joke
It grows bigger with each spell you cast, pings every opponent, and then turns into a colossal amount of mana ready to cast yet more spells
Scourge of the Throne gives you one when you attack the player with the most life, Hellkite Charger, and Aggravated Assault both give you extra combat by paying mana, and World at War, Waves of Aggression, and Relentless Assault are all sorceries that give you extra combat (the former two being able to be used twice)
A lot of balance and care goes into choosing the cost of a card, more than I can express here, but looking for similar effects on existing Magic cards can give you an idea of a fair costfor example, a ramp spell that puts two lands into play ought to cost 4 mana, per Explosive Vegetation