I would agree with charlie, I have used Inez, auction house and have recommended to people.
At the end of the day the price is what one is willing to pay/accept, you demand or reserve what you like.
Like any auction houses, cars, cattle etc,etc. The seller will be advised what the market can take but if the vendors wants to keep a higher reserver than its their choice.
No auction house likes their items to be unsold its bad for their cash flow and reputation and would like to value the property at a price that can be sold.
The cost that Katy talks about is to produce the catalouge. It is small in comparison to the value of the properties.