Computing Standard Profit Per Unit (Absorption Costing)

Hi. Thank you for your lectures. I find them very very useful.

Is there a rationale underpinning why Variable Selling Cost is not used in computing Standard Profit Per Unit when using Absorption Costing; i.e. (Selling Price – Unit Cost of Direct Material – Unit Cost of Direct Labour – Unit Cost of Variable Overhead – Unit Cost of Fixed Overhead = Standard Profit Per Unit)?

On the contrary, in Marginal Costing, Variable Selling Cost is used in computing Contribution (Standard Profit Per Unit); i.e. Selling Price – Unit Cost of Direct Material – Unit Cost of Direct Labour – Unit Cost of Variable Overhead – Unit Cost of Variable Selling Cost = Contribution (Standard Profit Per Unit).