I don't believe this has been advertised, even on the Jetstar specials page. The current best offer is $149 one way, however I've tried various dates in their booking engine right through from 9 August to 7 December… it's offering fares of $129 one-way. It'll be interesting to see whether it's withdrawn or belatedly advertised.
http://adioso.com/au/perth-au-to-denpasar-id-return-about-1-…