This links a gr:Offering to a gr:PriceSpecification or specifications. There can be unit price specifications, payment charge specifications, and delivery charge specifications. For each type, multiple specifications for the same gr:Offering are possible, e.g. for different quantity ranges or for different currencies, or for different combinations of gr:DeliveryMethod and target destinations.
Recommended retail prices etc. can be marked by the gr:priceType property of the gr:UnitPriceSpecification.