According to the AusTenders site, and filtering by department for Australian Bureau of Statistics, and looking for contracts signed from January 2015 onwards.... An estimated $4,812,088.16 was spent on server infrastructure and network equipment specifically reported as being acquired 'for Census'.
Of that $4.8M, $586,242 was spent on 'Load Testing Services' also annotated as 'for Census'.
But the cherry on the cake was this.... CN2641301, $9.6M in server infrastructure which presumably was the backbone of Census 2016 which could reportedly handle 1M form submissions an hour.
CN2641301 - Design, development and implementation of eCensus solution 2016 - $9.6M
CN3344945 - Load Testing Services for Census 2016 - $90K
CN3315542 - Load Testing Script Development Services for CENSUS - $34.6K
CN3344757 - Software Licences to support Laod Testing services for Census IT products from HP - $82.2K
CN3312448 - Licenses for Census Load testing - $325K
CN3356295 - Load Testing Services for Census 2016 - $54K
CN3325298 - 2016 Census Script Development - $51.9K Tender
CN ID CN3344757 lends to the possibility that Hewlett Packard Enterprise Performance Center software was used to conduct the testing, and a subsequent tender CN ID CN3356295 was the actual functional test of Census 2016 system.
Looking at the Tender the presumed conduct of testing was from 28th of June through to the 27th of September, much too late to be affecting an engineering level change to a system going live within 30 days. The takeaway from this, do not leave your Stress and Load Testing to the last minute.