A lot of owners overvalue their property in their mind. Mostly because they overspent on the property and trying to recoup the cost there, or they were fed wrong / outdated information from the media.
As a result, for the REA to get businesses they need to inflate the sold price expectation so the owner will sign up.
because it is overpriced, it will sit in the market for weeks, if not months, and the REA hopes that by that time vendor's expectation will wear down somewhat, and the REA can make the deal in the middle of the range.
from what I have observed, it is common for obviously overpriced property to drop price by 10-30k during the first week of listing, may be because there are no inspection / enquiries at all...
then for a further, real drop of the price it will take at least 1-2 months for another 2-3% drop in price.
Once it is sold at a low price, it is bad vibe for the REA if they list the low sold price in the web-site because no owners will want their property to list with them. so they will list it as sold - price withheld etc etc. so if you see price withheld you can safely assume they are sold at a low price, coz it is of the best interest of the REA to list high sold prices !
another point to note is as a buyer I will never tell a REA any information, because if you tell them you are FHB with 600k to spend, they will always give you overpriced 500k property for you to look at.
disclose anything to them will not help you get the property you want, at a good price.