Diagnostic Controls & Presets Auction Buyer & Consignor Payout Engine
Diagnostic Forensic Readings
Forensic Attribution Diagnostic
Real-time metallurgical and die variety cross-examination verified against certified populations.
Technical Breakdown: Physics, Metallurgy & Die Diagnostics
Public numismatic auctions operate under a dual fee structure where the auction company charges both the buyer (via the Buyer's Premium) and the seller (via the Consignor Commission). Understanding the exact mathematical gap between what the winning bidder pays and what the consignor takes home is essential for establishing profitable bidding ceilings and negotiation strategies.
Cbuyer = Hammer + [ Hammer × BP% ] + [ (Hammer + BP) × Tax% ] + Shipping & Insurance
Where:
• Standard Major Auction BP: 20.0% (Heritage, Stack's Bowers, Goldberg)
• Online Specialized Platform BP: 12.5% (GreatCollections)
• State Destination Sales Tax: 0% to 10.25% (Subject to state bullion exemptions under the 2018 South Dakota v. Wayfair Supreme Court ruling).
Payoutseller = Hammer - [ Hammer × Commission% ] - Reserve_Fees - Grading_Fees
While consignor commission rates on common lots under $1,000 typically range from 5% to 10%, high-value consignments over $25,000 routinely negotiate a 0% commission (with the auction house profiting solely from the buyer's premium).
Documented Benchmark Auction Records
Bidder placed winning $30,000 bid. With 20% buyer's premium ($6,000), total invoice was $36,000. Seller with 0% rate received full $30,000 payout.
With GreatCollections' 12.5% buyer's premium ($500), buyer paid $4,500. Consignor received $3,800 net after 5% seller fee ($200).
Pinnacle early rarity hammered at $100,000. 20% buyer's premium ($20,000) generated total invoice of $120,000.
Frequently Asked Questions
What is a Buyer's Premium (BP) in coin auctions?
A buyer's premium is an additional percentage surcharge added by the auction house to the final winning hammer price, paid by the buyer. At Heritage Auctions and Stack's Bowers, the standard BP is 20%; at GreatCollections, it is 12.5%.
How does state sales tax apply to coin purchases?
Following the 2018 South Dakota v. Wayfair Supreme Court decision, auction houses must collect sales tax based on the delivery destination. However, over 40 states offer sales tax exemptions for rare coins and precious metals, often contingent on reaching a dollar threshold (e.g. $1,500 in California, $500 in Florida).
Can consignor commission rates be negotiated?
Yes! While standard consignment contracts list a 5% to 10% fee for ordinary lots, sellers consigning high-value collections ($20,000 to $100,000+) can regularly negotiate a 0% commission, or even a 'hammer-plus' bonus where the auction house rebates a portion of the buyer's premium to the consignor.
What hidden fees can reduce a seller's net payout?
Consignors should watch for: (1) Reserve fees (charges applied if your lot fails to sell at your reserve price); (2) Professional photography or cataloging fees; (3) Third-party grading/reholdering fees charged back to the consignor; and (4) Withdrawal fees if a lot is removed prior to sale.
Why does GreatCollections charge a lower buyer's premium?
GreatCollections operates exclusively online with high inventory turnover and lower administrative overhead than traditional live ballroom auction houses, allowing them to charge a competitive 12.5% buyer's fee.
How do credit card payment fees work at auction houses?
Most major auction firms accept e-check (ACH), bank wire, or paper check at face value, but charge a 2.5% to 3.5% convenience fee if buyers settle their invoice with a credit card.
How do I calculate my maximum bid before the auction starts?
Take your total desired out-of-pocket budget, divide by (1 + BP% + Tax%), and round down to the nearest auction increment. For example, with 20% BP and 6% tax, divide your budget by 1.272 to find your strict hammer bid limit.