Variant prices override base price when applicable

When a variant has a custom price but the display and cart always use the base product price, customers see one price on the listing and are charged a different amount at checkout — or variants intended to cost more (e.g., XL size surcharge) are sold at the base price, creating a revenue shortfall on every sale of that variant. ISO 25010:2011 functional-correctness requires that price-affecting selections are reflected consistently across all display and calculation contexts. A product page showing $29.99 and a cart showing $24.99 erodes trust even when the error favors the customer.

Centralize variant price resolution in src/lib/pricing.ts so all display components and cart calculations use a single source of truth.

export const resolvePrice = (
  product: { price: Decimal },
  variant?: { price?: Decimal | null } | null
): Decimal => {
  if (variant?.price != null) return variant.price
  return product.price
}

Import resolvePrice in src/components/product/ProductCard.tsx, src/app/products/[slug]/page.tsx, and src/components/cart/CartItem.tsx. Do not inline the fallback logic in each component — divergence between components is how this bug reappears.

• ID: ecommerce-catalog.variant-pricing.variant-price-override

• Severity: high

• What to look for: Count all price display locations in the codebase: product listing components (src/components/product/ProductCard.tsx), product detail pages (src/app/products/[slug]/page.tsx), cart line items (src/components/cart/CartItem.tsx), and API responses. For each location, check whether variant-specific prices are used when a variant has a custom price, or if the base product price is always displayed regardless.

• Pass criteria: If a variant has a custom price field, that price is used in at least 1 display location and in cart calculations. If a variant has no custom price, the base product price is used as fallback. Count all price display locations and report: "X of Y price display locations use variant price when available."

• Fail criteria: Variant prices are ignored in all display and calculation locations — the base product price is always used even when a variant has a different price.

• Skip (N/A) when: No variants have custom pricing fields in the schema — confirmed by examining the variant model and finding no price-related field.

• Cross-reference: For price display formatting, the Geo-Readiness audit covers locale-aware currency formatting.

• Cross-reference: For cart calculation accuracy, the Pre-Launch audit covers order total correctness.

• Cross-reference: For pricing consistency across views, the Performance Core audit covers data consistency in cached vs. fresh renders.

• Detail on fail: "Variant schema has price field but src/components/product/ProductCard.tsx always displays product.price instead of variant.price" or "Cart in src/components/cart/CartItem.tsx uses base product price instead of variant price"

• Remediation: Use variant price if present, fall back to base price in src/lib/pricing.ts:

  const getPrice = (product, variant) => {
    if (variant?.price) {
      return variant.price
    }
    return product.price
  }