When calculating the Standard Cost from a SKU with replenishment system production order.

If the BOM includes a purchased Item (Variant) - use the cost from this Items SKU in the calculation.

Repro (without Location):

Create 1 Item with 2 Variants. - Costing Method FIFO

Create Stockkeeping units for both variants.

Set replenishment system to purchase on item and Stockkeeping Units.

Purchase, Receive and Invoice some of both Variants and let Variant 1 have a different price than Variant 2.

Create 1 Item with 2 Variants. - Costing Method Standard

Create Stockkeeping units for both variants.

Set replenishment system to production order on item and Stockkeeping Units.

Create 2 Production Boms - BOM1 using Purchase Variant 1, BOM2 using Purchase Variant 2.

Add Production Bom on the 2 Production Stockkeeping Units. BOM1 on Production Variant 1 and BOM2 on Production Variant 2.

Calculate Std. Cost for each SKU - and you will see that the cost is calculated with Item Cost and not with SKU Cost.