Why does the same size portion cost more when it is on the premium side of the menu board

The pricing side is real too and it has a name. A more expensive item on the board makes everything next to it look reasonable, which is why the premium option often sells less than it appears to be designed to sell. Its job is partly to be the thing you decide against.

I worked in a chain kitchen and the portioning rules for the expensive proteins were completely different. Everything else was a scoop, the expensive one was counted by piece and weighed at close, and waste on it was reported separately. That alone tells you where the margin risk sits.

Mostly ingredient cost, and the multiple is bigger than customers imagine. Chicken thigh, shrimp and beef are not in the same price bracket per kilo, and shrimp also loses weight and yields badly once it is peeled and cooked, so a same sized scoop of it can cost the kitchen several times what the chicken one does. The surcharge is a round number because it has to be readable on a board and typed into a till by a nineteen year old at lunchtime rush, not because it was reverse engineered from the invoice.

I think the psychology explanation is doing too much work here. Every kitchen I have seen prices from a spreadsheet where each dish has to land inside a target food cost percentage, and the premium items are simply the ones that cannot land there at the standard price. If it were mainly a decoy, they would not portion the shrimp with a scale while the chicken gets a scoop.

Same box, different contents, different cost. The surcharge is the honest version, the alternative is quietly shrinking the scoop.