Thanks for asking. In 1985 a Sydney Taxi plate cost $78,000. Today they are selling for $430,000, someone else can do the math on that. A lot of my friends got into this and profited very well on cab plates. As for how it compares with other investments, again someone else can do the math on that.
Right now my best passive income investment is my rental unit on the Northern Beaches of Sydney. I pick up a nice tidy rental sum each and every Month and do absolutely nothing for it (except put in my tax return each year). In fact I haven't even looked at the property in 3 years now, that's passive.