I was going to say the same. Collectors will hold *many* firearms. As will range armourers.
Farmers and contract shooters are restricted to 10 across all calibres and types. Hunters to 4.
I know people with numbers, but they are (or were, and remain licensed to be) contractors.
My Mum collects minature porcelain plates. Collecting firearms is no more unusual. I think Australia as a society is somehow conditioned to fear firearms, which is a bit silly.