I get that from a balance point of view. however its not logical imo, the best way to balance the power of a gun against a sword or a spell would be that guns are expensive/ ammo expensive so that wasting ammo on weaker enemies would not be to the players benefit and encourages them to use more than just the guns to succeed.
Problem is, magic isn't logical to begin with. So tech negating magic or magic negating tech isn't less logical than what things cost.
And if I remember right, the tech stuff in Arcanum was pretty damn expensive.
(No longer replying to quote)
Also, magic mixed with tech is not steampunk, and neither is fantasy mixed with tech. Steampunk is Victorian era tech mixed with modern day tech.
And yes, I would play a fantasy game with guns, and I don't think many people would have a problem with it.
And it's not really that rare... WoW has it.