I mean, the spiders in Australia are already enormous. I can't imagine what an eeeeeeeenormous Halloween spider would be by those standards.
There were a lot of large-ish hairy spider decorations around here, too. But not enormous by American (even Texan) standards, so probably not what you encountered.
The basic rule in Australia is the larger the spider, the less dangerous it probably is.
Don't listen to Dr Trewin, he's not a toxicologist.
The decorations I've seen were approximately hand-sized spider body with legspan about a foot across. I asked my spouse for a more accurate estimate and he mumbled something about flamethrowers...
Flamethrowers! Completely relatable.