Regular auctions, whether Taobao or auction companies, will inform you of the commission ratio. The entrusted auction contract or auction instructions will remind you that different auction items have different commission ratios. The ladder you mentioned may be a judicial auction.

Article 32 of the "Provisions of the Supreme People's Court on the Auction and Sale of Property in Civil Execution by People's Courts" stipulates that if the auction is successful, the auction agency may charge the buyer a commission according to the following ratios: For auction prices below 2 million yuan, the commission ratio shall not exceed 5%; for the part exceeding 2 million to 10 million yuan, it shall not exceed 3%; for the part exceeding 10 million to 50 million yuan, it shall not exceed 2%; for the part exceeding 50 million to 100 million yuan, it shall not exceed 1%; for the part exceeding 100 million yuan, it shall not exceed 0.5%.

But this is rarely used now.