When you registered to bid you confirmed the following:
I agree that I have read and understood Bonhams' conditions of sale and I wish to be bound by them, and I agree to pay the buyer's premium and any other charges mentioned in the notice to bidders. I understand that this affects my legal rights.
For all Sales categories excluding Wine:
Buyer's Premium Rates
25% up to HKD800,000 of the Hammer Price
20% from HKD800,001 to HKD15,000,000 of the Hammer Price
12% over HKD15,000,000 of the Hammer Price.