UNNEST is a deliberate one-to-many — parent-level metrics summed after exploding are multiplied by list length.

Exploding an array changes the table's grain from parent to parent×element — that's the point — but every parent column rides along, copied once per element, and any aggregate over those copies counts the copies. It's the P06 flagship in modern clothes, with one difference: here the fan-out was chosen, which makes it feel safer and land more often. The discipline is a grain sentence before the SUM.

SELECT
  SUM(price) AS revenue
FROM
  (
    SELECT
      panel,
      price,
      UNNEST(colors) AS color
    FROM
      panels
  );

SELECT
  SUM(price) AS revenue
FROM
  panels;

The panel revenue summed to 78, not 48 — after UNNEST exploded each panel's color array, its price rode along once per color, so SUM multiplied it by the list length.

Aggregate at parent grain first and join back; element metrics on the exploded table, parent metrics off it.