I think real estate agents prefer filling their auctions with a cast of extras aka buyers who don't have a slight show of winning. Someone I know is now in the process of buying a home, and has been in an identical situation bloody twice! The last house's CV was $660k and the listing on Trade Me came under $700k.
Every time she spoke to the agent, she was assured it was in her budget (up to $750k) and was strongly encouraged to come to auction. After spending time and money on the homework, and taking time off work to attend the auction, she found the opening bid was $860k and final price $895k.
She spoke to the agent on the day of the auction. The agent already knew the level of the pre-auction offer yet still insisted her to come. She feel it is unethical at the very least, and would not deal with that agency again. I wish a real estate agent would write in and have a crack at justifying this practice. Yeah right.