Oddly enough (perhaps not in Australia but definitely here in the US), the cheese does not appear to be melted (?!). Of course, KFC doesn't serve nachos here in the US.
A Nacho Box goes for $3.95 AUS (~$3.60 US).
To complete the theme, there's also a new Nacho Burger, which actually has nacho cheese sauce in it. Along with the cheese sauce is a crispy chicken breast filet, corn tortilla chips, salsa, lettuce, and a slice of cheese.
The Nacho Burger is a bit pricier at $6.45 (~$5.88 US).