Shipping is calculated based on the weight of the products in the order from the same store. This can mean when purchasing multiple products at the same time from the same store, the total order weight may be classed as bulky. TheMarket does not determine the shipping costs charged by the store for orders classed as bulky.
For example with MarketClub+ :
2 x 7kg barbell - ships free when order value is $45+
5 x 7kg barbell - total weight is considered bulky. Shipping is $63