[jdp23]

> A utility function or cost/benefit tradeoff isn't a matter of opinion.

Well, they're both contextual and subjective; different people looking at the same utility function or tradeoffs will come to different conclusions. Maybe we mean something different by 'matter of opinion'.

> studies show that people have cognitive biases which induce them to select the wrong choice.

Studies (done by people with specific cognitive biases according to conventions defined by people with specific cognitive biases) show that participants make choices that they authors of the studies consider "wrong" or "suboptimal". As you say, the power of cognitive biases should not be understated.