That alters the value. It's your script for the auction yourself. She suggests holding onto catalogs to use as a reference when you go to other auctions. If you see an item similar to one you've seen elsewhere, you can comparison shop. Smaller auction houses may publish a catalog for purchase before the auction, or just print a free list of lots for sale.
People can make emotional decisions.
I've been known to go beyond that. I've also been the object of dealers upping the price. I bought a brass headboard and footboard, and they were bidding me up and I got carried away and paid more than I should have. It's easy, when you're bidding, to lose track of everything but the object of your desire. You're proving that you can have an impact on the worth of this item.