Hammer price, buyer's premium, and what a wine really sold for
Two houses report $1,250 and $1,170 for the same wine. Both may have hammered at $1,000. Here is how a published result comes apart, and why LastHammer shows the hammer price per bottle.
Three numbers for one sale
The hammer price is what the winning bidder bid: the number the auctioneer's hammer falls on, or the closing bid in an online sale. It is the market's answer to what the lot was worth that day.
The buyer's premium is the house's fee on top, a percentage of the hammer price. It runs from 10% at K&L to 25% at Zachys, Acker and Christie's, and it is paid by the buyer, so the buyer's total is hammer plus premium (plus tax and shipping).
The published result is, at most houses, hammer plus premium. Zachys, Acker, Christie's and WineBid print the total; Hart Davis Hart and Spectrum print it at their own rates; Bonhams publishes at hammer. So two houses' results are not the same kind of number, and a table of "prices realized" across houses compares fees as much as wines.
The arithmetic
A published result of $1,250 at a 25% house is a hammer of $1,000 ($1,250 divided by 1.25). At a 17% house, $1,170 is also a $1,000 hammer. A lot of six bottles hammered at $1,000 is $166.67 a bottle; a magnum is two bottles' worth, so a magnum at $400 is $200 per 750 ml. That last step, per bottle at 750 ml, is what makes a case at one house comparable with a single bottle at another.
LastHammer does exactly that arithmetic for every sold lot in its file, using each house's own premium (with Spectrum's $10 minimum a lot), and shows the result: the last hammer price per bottle, the house and the date, and the average of the last three sales when there are at least two. The fourteen houses and the premium removed for each.
What the hammer price is not
It is not what you would pay to own the wine: add the premium, tax and shipping. It is not a retail price, which sits above hammer by the merchant's margin. And it is not an estimate: houses publish estimate ranges before a sale, and lots sell above, below and inside them every week. The badge shows sales, never estimates, and the watchlist email shows a lot's reserve or estimate, never a running bid, because bids move.
Why it matters when you bid
The question at a live catalogue is always the same: is this lot cheap? The honest comparison is the hammer price you are about to bid against what the same wine and vintage hammered at last time, anywhere. That is the number the extension puts under the lot title, and clicking it shows the sales it came from, so you can see whether the last price was one lot or ten.