Varanus gigantis the largests of the monitors in aus,also one of the rarest aswell.Price wise as ive only heard of them 4 sale never actually seen 4 sale i would expect they would be up round the $2000 a hatchie im only guessing.If you have that sought of money & the space that you will need to keep them i could maybe head you in the right direction.They are class 2 in nsw & generally people with them dont say they have them bit like the gtps,they grow to 1.6mtrs often seen over 2m.
They are by far my favourite lizard. They can be extremley aggressive when feeding. They are relatively slender compared to other large monitor species. They do best in large outdoor enclosures.
Also there was an article about them in the REPTILES magazine a few months ago