The Talos Principle hardly ever goes on sale outside the big Steam sales and when it has in the past, it was only 33% or less. With the release of the new DLC for this game yesterday, the developers put the main game on discount for 66%. Also the new DLC is discounted for 10% as well.
It was also this price during recent steam sale:
https://www.ozbargain.com.au/node/199494
Still, good price.