Dan Ariely, a behavioral Economics professor at Duke University's Fuqua School of Business and author of "Predictably Irrational," said the "better-than-average" effect is at play. And knowing your next-door neighbors sold their house for $500,000 makes it even more imperative for a homeowner to top that price.

"We feel that we're better than other people. We're unique. We're special," he said. "It stands to reason that our houses are also special."

The attachment to a house only intensifies the more a homeowner personalizes it, creating an extension of themselves.

"The moment we invest in something, we fall in love with it," Ariely said, which applies to something as sentimental as children or as trivial as origami.

That puts real estate agents in a precarious position of pricing a house to sell, but not insulting the homeowner by recommending a lower asking price. To a homeowner, a low, but realistic, listing price is "like someone calling your kids ugly," Ariely said with a laugh.

Nancy Batchelor, a real estate agent at Esslinger Wooten & Maxwell Realtors in Miami, says she usually agrees to list the owner's asking price as long as they can reevaluate the price in 30 days if the house doesn't sell.

"I would like to believe their house is different, but I also don't want to do them a disservice," Batchelor said.

Joni Herndon, an appraiser in Tampa, Fla., said real estate agents are calling her in to help homeowners grasp the reality of their home's value. Herndon frequently fields questions from disappointed homeowners after an appraisal, and has to explain how broadly the market is declining and why what a neighbor got two months before for his house doesn't apply anymore.

"But sometimes you just can't get through to people," she said.

She said homeowners who bought newly built homes at the height of the boom are the most stubborn, because they're trying to get back every penny they spent on customized changes.

One homeowner Herndon did an appraisal for refused to lower her listing price for the third time, insisting that such features like a raised roof and more space between two windows in an upstairs bonus room set her house apart from others just like it.

"It's the mine is better than yours mentality," Herndon said.

The homeowner originally asked the builder to move the windows another foot apart and raise the roof by 12 inches so the wall could fit her big-screen television. She also spent $15,000 in extra landscaping and exterior lighting, and $2,900 on designer fans, Herndon said.

"You could have put $1,000 worth of fans in the house and blown just as much air," Herndon said. "Owners are very concerned about how much they paid for particular changes, but buyers out there don't value them."