Has been around $3,500 on previous deals - see link https://www.ozbargain.com.au/product/sony-bravia-kd75x8500d
This deal at Bing Lee should make it of similar in value as you receive $399.50 gift card. Not sure if there is scope for some further haggling, will try.
Part of Bing Lee wide promotion on all 4K TV's. Receive 10% gift card.
https://www.binglee.com.au/tech/tv-video/4k-ultra-high-definition?intpromo=homepage|homepage-banners|position5|bonus-gift-card-on-4k-tvs
Also have the Samsung Series 6 75' JU6400 UHD LED TV for $3,495 with the 10% gift card.
https://www.binglee.com.au/samsung-ua75ju6400-75-uhd-led-tv