You can explore this site: eweb.customs.gov.tw/lp.asp?ctNod … &BaseDSD=7
If you check the link for Tax relief and Tax calculation:
1.Tax relief is granted on postal articles (excluding tobacco and alcohol) up to a Customs value of NT$3,000.
2.For miscellaneous postal articles with Customs value over NT$3,000 but not exceeding US$20,000 (margin for waiving Import Permit), a 5% flat rate of import duty will apply.
3.If more than two mail shipments are sent from the same place to the same person or the same address at the same time, their FOB value or Customs value shall be summed up as a whole.
4.If mail shipments are sent to the same person or the same address frequently during a certain period of time, the case shall be deemed as circumvention and the above mentioned duty exemption privilege shall not apply.
5.Advertising articles and samples, with Customs value not exceeding NT$12,000, shall be exempt from import duty.
6.Customs also collects other taxes and fees on mail shipments entrusted by other government agencies, e.g. commodity tax, business tax, tobacco & alcohol tax and trade promotion service fee.
I am pointing you in the direction for an answer and do not take the above as a definitive answer. You are technically dealing with a regulated product category so laws and regulations can get a little difficult sometimes if someone decides that they should be - especially at the postal point of entry.
An example from another product category: you can bring in a certain amount of tobacco duty free; you can also bring in a certain amount of tobacco for personal use but pay the taxes and duties owing; there is a threshold though (and a low one) where you cross from the personal use level to a requirement that you be licensed.