If you have not exceeded the limit on the receipt of international postal items, the customs duty you pay.
To get the latest information about the monthly limits, fees and rules of customs clearance, please contact the relevant customs Department in your country.
Also worth considering that the customs control during the inspection of the packages takes into account the cost of the order before discount.
I also want to warn that customs may ask you to pay the service charge or taxes when the order will pass the customs clearance.