If we live in a free market system wherein products are priced according to what the market will bear, then there really is no better way to determine value than auction. This idea holds for any good or service but seems particularly true with respect to setting prices for artwork, an area with which many buyers often seem to struggle. 

Because they represent the public domain and are by definition therefore transparent events (as opposed to 'secret pricing'), prices set at auction are more trustworthy conveyors of value. They are often the best way for consumers to increase their comfort buying art on the internet because of the availability of comparables. It's far easier online to research the pricing history of work by artists you're considering, as well as that of artists at similar points in their careers.

Many non-profits are now taking their fundraising events to online auctions in efforts to increase the potential pool of bidders, as well as provide an important degree of privacy to both seller and buyer. Not to mention the convenience and ability to offer a range of items unconstrained by physical capacity.