My comments are included in Maxwell Rabb's article published today in Artsy. The article provides a clear and useful summary of the fees associated with buying and selling art at auction.

My quote is about the vendor's commission:

A seller’s commission is a fee charged to the seller by the auction house for its services. A seller’s commission is usually charged at a rate between 5 and 10 percent.

Seller’s commissions vary from lot to lot depending on an array of factors: the value and desirability of the work, the competitiveness of the consignment, the seller’s relationship with the auction house, and the financial structure of the sale (like guarantees or marketing costs). High-value or prestigious lots often receive lower or waived fees to attract them, while lower-value or riskier works carry higher commissions to cover costs.

“They’re more likely to enforce a seller’s commission on a low-value work,” said Shapiro. “For a high-value piece, they’ll do what they can to get it, since they’re probably competing against other houses.”

Some categories—like design, wine, and online-only sales—carry their own rates. Even within the same auction house, London and New York may apply slightly different terms.