I dont know if it is the same all over but here we get charged by weight.
0-3 kg package is one price 3-5 kg another
When I set this up I got a product with a weight of 3kg costing 3 times the amount I had specified for 0-3 kg. And when I look at the code it is multiplied by weight wich is totaly wrong for how it works here. It dont mather if the weigh is ,5kg or 3kg it is the same price to send anything within 0-3kg.