As far as monthly subscriptions go, Nintendo's online service - while not as good a deal overall as PlayStation Plus or Xbox Live Gold - was relatively affordable. But it's just gotten even cheaper, after Twitch announced that Twitch Prime subscribers would get a year-long subscription to Nintendo Switch Online as a bonus.
The deal is available to Australians, as per Twitch's FAQ, and it's available even if you have an existing Nintendo Switch Online subscription.
How it works is this. If you don't have an Twitch Prime subscription, you'll be able to start with the free 30-day trial, which then gets you access to three months of Nintendo Switch Online access. Once your Twitch Prime account has been active for 60 days - a move designed to stop people from exploiting the free period - you'll be able to redeem an additional six months of Nintendo Switch Online access to your account.
It's worth noting that if you decide not to continue with a Twitch Prime account, but claim the three-month Switch Online access, you'll automatically be set on a recurring three-month subscription plan for Switch Online. That can be cancelled at any time, but it's worth pointing out so people don't forget. The only kicker is that you can't redeem the Switch Online bonuses to family Nintendo accounts - it's only valid for individual memberships.
You also might already have Twitch Prime without realising it. The premium account is included for free as part of the Amazon Prime subscription, which costs $6.99 a month or $59 a year. Switch Online is only $29.95 a year or $5.95 a month, so if you don't have Amazon Prime you're not saving money, but if you've already signed up to Amazon then it means you can at least save a little extra by not paying double for a recurring Switch service.
More details about the deal, and how to redeem it on your console, can be found here.