Why there is no cost per weight
A weight-based rule would be one Soran could not evaluate. The order data Soran stores carries no weight, so a rule that depended on it would silently apply to nothing. If your real shipping cost scales with weight, a flat rate set to your average is the honest approximation, and a per-destination split usually captures more of the variance than weight does anyway.Related
Expenses and profit
The other kinds of cost.