RPM question

[nudj]

I've been thinking of using RPM in a fantasy game. Looking at GURPS Thaumotology RPM, i see that Fireball is a greater create energy effect and costs 6 points per +1d. I also see that lesser destroy body causes damage at 2 points per +1d if the tech in the setting allows that level of damage from a hand held or ranged weapon.

That's a big difference in cost. Can I apply the setting rule to a fireball? Even in a TL 3 game, 12 fatigue for a 2d fireball seems ridiculous.

Thanks

nudj