The difference between, "You cannot use your power on him (or in this area) at all, period," and, "It's very difficult, but possible, for you to use your power," is a significant one. In my experience, complete static is easily worth twice as much as resistible static. GURPS seems to agree, at first glance. Simulating this with a -50% limitation works by itself, but when you throw a couple of enhancements on there (such as the Area Effect which is de rigeur for building a "screamer") the cost difference quickly changes to a flat 15 points.

I posit that if the ability to completely shut down every psi within 128 yards, no matter how skilled or powerful they are, is worth 150 points, then the ability to merely make it difficult for them to use their psi should be closer to 75 points than to 135 points. The way to achieve this is to change the base cost, so Static (Resistible) is 15 points and Static (Complete) is 30 points.