Historically, auctions are wholesale events. 90% or more of the people involved in auctions are looking for investment potential.
An acquaintance and friend of a very good friend owns a local auction house. He is a great boondoggler, and travels the world moving booty from estate sales to his San Antonio auction house.
The Great Texas Auction House - Vogt Auction Galleries
His Tuesday night auctions are attended by antique dealers from all over the state, and they quit bidding what they perceive as a reasonable wholesale price. It's a fantastic place to buy antique furniture, and I've scored a few great pieces there on Tuesday nights.

Likewise, ebay is supposed to be the nation's garage sale.
Everything I have ever purchased in ebay auction was at a price that I knew I could resale for greater.
Buying with a sniping program lets you stick to this philosophy. You won't win everything, but what you win will be at the price you Want to pay.