What you're seeing on the Listing is information provided to REA from RP Data.
As per the below screenshot, REA acknowledge when the info is provided by RP Data, to limit any confusion on where the data is coming from.
This is due to an agreement that RP Data have recently put in place with REA which allows them to mine data from Sold Listings on realestate.com.au.
For further info here, the best recommendation is to touch base with REA to request the price be removed, or changed to read as 'Contact Agent'.
Domain.com.au are taking similar actions to those of Realestate.com.au & have started to advertise Sold data on Listings in their 'Sold' section. The difference here is that the Sold data showing on Domain Listings has been provided by APN Pricefinder.
Domain are also acknowledging where the data has come from, to avoid any confusion here.
If you'd prefer to have this removed, or updated to read differently, you'll need to contact Domain directly to request this action be taken.