Valuation on basis of transaction value(section 14(1)}

It says that valuation of goods for levy of custom duty shall enclude cost

commission and brokerage 


design work

royalty and licence fees

cost of transportation to the place of importation

insurance ,loading and unloading  and hanling charges

my query is seller who is importing goods has already enclude the above charges while calculating cost per unit.

then why above expenses are further added to arrive at transaction value.Its already encluded at cost.

please answer query i need your support