The claims seems to be roughly correct in the sense that the TAPRI report has this data; from the report linked by Legion600:
Table 2 shows that at the time of Census in 2016 these temporary migrants constituted a
significant share of all those employed in the occupations listed. For example, this amounted
to 19 ...
No, Victoria doesn't have the highest power prices in Australia. Not by a long way.
Domestic energy plans in South Australia (incidentally, currently under a Liberal government) are about 30% higher according to this comparison of various states and energy plans. The basic energy price in South Australia is about 50% more per kWh.