Can you lower the cost of goods when shipping by mail?

We cannot underdeclare the value of goods when shipping by mail for the following reasons:

Legality: Underdeclaring the value of goods in declarations violates customs laws both in the country of origin and the destination country. This is considered fraud and can lead to serious legal consequences, including fines and criminal prosecution.
Risks to the recipient: Underdeclaring the value can lead to problems for the recipient of the goods during customs clearance. This may include delays, additional inspections, and even confiscation of goods.
Insurance: Insurance payouts for losses or damages during transportation are based on the declared value of the goods. Underdeclaring the value can result in a reduced compensation in the event of damage or loss.
Tax reporting: We are required to provide full reporting on both purchased and shipped goods from Japan to the Japanese tax authorities.

Additionally, we regularly receive requests from customs authorities that require us to provide documents verifying the payment for the goods at the value stated in the invoice upon shipping. Given all these factors, we cannot underdeclare the value of goods.