Glaser Safety Slugs for pistols will kill the targeted one with minimal danger to those in the close vicinity, but they cost $US1.60 or so each.

I know they are "expensive" at $1.60 each, but with some budget modifications, and fiscal restraint, NSW might be able to afford say two.
p/s Is there any discount for buying two or more?

I do not know

(but it seems some details are in the public domain)

but were they using other firearms apart from pistols and are there safety slugs available for them also?

o sung wu,
I came into the job just as Delaney was leaving around 1961 or 62. But he live in Milson's Point
and was a mate of my father who had a few no bills generated through the man.
Any corruption in the job is bad regardless of how petty it is.
The Vietnam war came along and off I went believing I was doing the right thing. Silly me.
So I read now mate that there are more guns in the country now than there were when they
recalled them. Some bloke up here got busted with an AK 74 in his garage.
Said it was for protection against Islamic State infiltrators. I wonder where he got it.

Herter's® Defense 12-ga. Rubber Buckshot

Rubber buckshot for nonlethal self-defense and animal deterrence. Not for use in semiautomatic shotguns. Loaded in Italy to the highest standards in consistency and reliability, Herter’s has the perfect load for home defense or practice at the range. Using high-quality powder, shot and hulls, these unique loads deliver excellent dependability and performance at an affordable price. Per 10.
$5 shipping on orders of $99.
that's 90 cents for Oz, 22 shots at Lindt = $19.80 per terrorist.

As the Royal Commission into home insulation was $20mill for 8 months, the Lindt Inquest of 6 months must have been $15 mill.
The cost of explosives at $19.80 was worth 13.152 seconds of the Inquest. This fits well with 12.48 seconds for women's 100 metre hurdles at Rio and 13.05 seconds for men's 100 metre hurdles. The gun used is harmless pistol cost unknown.