I'm experiencing more and more challenges with the current way shipping cost for multiple items is handled. Currently I have no choice than to either significantly overcharge customers that order 2 items or eat a significant loss when a customer orders 3 items or 2 items with an option that adds 1oz.
1 item: 5oz (incl. packaging)
2 items: <8oz
3 items: 11oz
2 items w/ option: 10oz
First Class international shipping excl. Canada is roughly $12-13 for 4-8 ounces, and jumps to $20-22 above 8 ounces.
Even worse when you have multiple products with different weights in your store. Will the base rate be charged twice when a user orders both? I.e. $24 in the above example? Or the additional rate picked randomly from one of the two?
In conclusion, I completely agree with maxtc that the current solution while simple is not practical. At a minimum there should be a weight per product and option on the product page, and then a base fee plus cost/weight schedule for each shipping rate.