[malloyd]

No. Nor are they less fair. The central problem is the *modifers* aren't fair. Many of them simply differently beneficial or crippling on different powers, and therefore any system that offers a fixed modifier - whether it's additive, multiplicative, flat cost or anything else - will fail to generate "fair" prices relatively frequently.

You can't "fix" this with a change to a mathematical system of computing costs. Not even for unmodified traits - because the usefulness of absolutely identical abilities can vary wildly with the details of the setting. That's why basically every rule system that ever included a build-your-own ability subsystem has included a GM vetting process or vaguely defined sliding scale modifier he can use to adjust them. Rules lawyers hate those sorts of meta-rules and ignore them, but game designers have been aware of the issue since forever, and know it's fundamentally unfixable with mechanistic rules - it needs a judgement call.