Independent based property valuer Chris Egan said rural properties in some areas have witnessed a huge rate-per-acre increase.

"Rural property in some areas of the Riverina has increased by about 50 per cent in the last few years," Mr Egan said.

"Each off-the-market sale would would potentially obtain a high level of demand if it was freely exposed to the market.

"So many rural properties are selling above the market value and these properties only come up once a generation, so when the right property comes on the market people act quickly and are prepared to pay a premium to obtain neighbouring properties."

Mr Egan said rural properties often choose to sell off-the-market because they don't want to attract commercial companies.

"A lot of long term rural land holders choose to sell off-market so they can select the purchaser and sell to neighbouring families as opposed to commercial companies," she said.

"People are prepared to pay a premium to obtain neighbouring properties.

"Despite being in the face of a terrible or prolonged drought, rural producers think long term rather than in the short term as they know it will start raining again."

Ray White Rural director Geoff Palmer said this market has been particularly healthy in southern NSW.

"Typically, off-market sales are coordinated via this method to protect the privacy of vendors and buyers," he said.

"This market has been healthy for the $10 million plus end but sales do tend to take a longer amount of time to close.

"I am positive for continued demand for our market here in the Riverina and I believe the buy side of the transaction is navigating the tightening credit quite well."

However, Mr Palmer said he does not think there is any threat from commercial companies purchasing land.

"A sale typically represents a willing vendor and a willing purchaser," he said.

"We do conduct off market sales, however it is in my experience that properties that are advertiser in a way to ensure buyer competition make the best money.

"In the case of an off-market sale, confidentiality can be assured, but market premium cannot."