Do you have a reference? What industry, what technologies, what city? I find established businesses in Melbourne, paying permanent senior software devs $120k-$130k, so I find it hard to believe that mid-level developers are getting paid $150k+, unless they're contractors in a somewhat niche field.
Sydney, large tech company (100+ engineers), highly competitive. $150k for a senior dev sounds right.
This is if you want the top engineers who are getting offers from Google and Facebook.