The 20% advantage
Vinfolio recently did an analysis where we examined the retail prices at which we sold wine compared to what those same wines sold for at U.S. auction houses (hammer plus buyer's premium). The average price advantage we achieved in 2007 YTD is 20% (22% to be exact but we rounded down). Please review Maximizing sales price on our site for details on the analysis, why this premium exists, and why our retail prices are still competitive for buyers.

Benefit to private sellers of wine
This pricing advantage translates directly into higher net proceeds for the seller (even when the auction house has no seller's commission).

Payment is also made in a few days (not months) because sellers are paid upfront, before the wine is even sold to consumers.

Why do people still sell at auction?
Mainly because that's the traditional choice (see The limited relevance of wine auctions). When sellers learn that it's faster, simpler, and more profitable to accomplish their goals via a different method, they pay attention. For example, we purchased a $600,000 cellar of impeccable provenance this month in direct competition with most of the New York auction houses.
Bottom line: If you're considering selling wine through an auction house, sell your wine to Vinfolio instead.