There is a Tang Soo Do martial arts club at Swinburne University (Hawthorn campus, Melbourne) that also allows non students to join. Tang Soo Do can be likened to a Korean version of Karate, but this particular club is more of a blend of Karate and Taekwondo. Rather than overload this post, the website has a lot more info.
I'm a student of this club and have to say it's been a pretty good deal already in past years, but this time there is no extra fee for non students to join (used to cost about $140 per year when you added that). I think it was too much hassle for the paperwork to differentiate the two.
They train twice a week, Monday and Thursday nights 6.30pm to 8.30pm, Thursday being the main class.
So $78 for the rest of the year works out to about 50 cents a class.
For those who live around Swinburne University at Glenferrie station in Melbourne there's also a cheap (compact) gym at the university sports centre.
Interesting. Usually sports clubs have to charge more for non students to cover the insurance fees etc.. that are usually included in student fees.
I can't say that advertising your club as being like TKD and Karate is appealing… but looking at the website I think you are right. A warning to people that these kind of clubs aren't very good if you want to actually learn self defence.