https://www.facebook.com/AdventureWorldOfficialPage/videos/2046686005352676/
Vid above indicates that it cost $14million dollars to build in 1982, but then almost acquired for $6m in 1999:
https://www.afr.com/property/leisurewide-takes-option-on-perths-adventure-world-19990128-k8iol
Michael Edgely's history was scrubbed from AW's website at the beginning of 2019:
https://web.archive.org/web/20180909214409/https://adventureworld.net.au/about-us/our-history/
https://web.archive.org/web/20190226043845/https://adventureworld.net.au/about-us/our-history/
Interestingly the same entity has owned AW's land since 1996 and purchased adjoining pieces of land for a song in 2006 and 2010.