Planning fallacy
The Sydney Opera House was expected to be completed in 1963. A scaled-down version opened in 1973, a decade later. The original cost was estimated at $7 million, but its delayed completion led to a cost of $102 million.
MLC Building, North Sydney
Completed at a final cost of A£4.5 million the MLC Building was officially opened by Prime Minister Robert Menzies on 22 August 1957, who expressed that "The view [from the top floor] gives me such a new conception of Sydney that quite frankly I'm beginning to like the place".