For NSW Residents Only
Promotion is called a "Sydneysider Pass".
If you pay for a 7 day flexiticket in March for yourself, and bring in NSW ID, you can have unlimited visits to Sydney Tower for the balance of the year.
Adult cost for flexiticket is $25 and child is $15
See the link for further details. Entry is just to the observation level, not the Skywalk, which costs extra.
http://www.sydneytowereye.com.au/tickets/sydneysider-pass/Value I listed is just made up, as it depends on how many time you visit the Tower.