Much has been written to date about the cost to produce green hydrogen and how this compares to other colours, such as grey hydrogen (extracted from natural gas, and emissions are released to the air), or blue hydrogen (extracted from natural gas, and emissions are captured using carbon capture and storage). 

The argument is that unless green hydrogen can come down in cost to below blue, it will struggle to get a foothold. A price on carbon would clearly favour green hydrogen, which is made without any carbon emissions, but there is not yet such a universal mechanism in many countries, including Australia.

Source: https://thefifthestate.com.au/