Shipping cost not calculated

When the shipping method is set to "total quantity of items", and the costs are mapped thusly:
(number of items:cost)
1:2.00
2:3.00
3:4.00
4:5.00
5:6.00
6:7.00
7:8.00
8:9.00
9:10.00
10:11.00

The shipping costs are NOT calculated for tangible products.