Cheapest cost to Singapore for 100g parcel

I have a parcel weighing 100g to be sent to Singapore. I went to a China post branch in Futian, Shenzhen. The lady behind the counter insisted that my package cannot be considered under small package. The cost that was told to me was RMB78 and takes 20 days. Can you confirm if she was right? And if you could suggest other economical way to sending small parcels from Shenzhen. Thanks.