Navigate to Data > Product Costs to see your cost per item in OrderMetrics:
All product costs are imported from Shopify directly. Make sure you have the 'Cost per item' updated in Shopify via Products > Specific Product > Cost per item:
Please note: product costs are synced with Shopify once-per-day at your local midnight. Any changes you make to product costs during the day within Shopify will update in OrderMetrics at 12am, your local time.