Love the perspective. If I understand correctly, it is similar to trying to determine the cost of true curation against best ROI. The premium then is the avg percent amount you give up to upvote something not ROI based. Considering the variable nature, this particular question does come down to psychology as you've said, as curation rewards are there to essentially offset the mental predicament.
You can always get more with calculated efforts, so then the difference between time spent curating and ROIing correlated with that premium could be said to be what, a core game care score lol, I don't know where I was trying to go with anything, but cool read.
RE: Math of Steem: Can I characterize the premium value I place on my outgoing vote?