Australian National University has run seven scenarios on the likely worldwide outcomes of the SARS-CoV 2 viral pandemic.
Best case scenario (low severity model): Global GDP loss of $2.4 trillion with an estimated 15 million dead.
Worse case scenario (high severity model): Global GDP loss of $9 trillion with an estimated 68 million dead.
These models used the 1968-69 Hong Kong flu pandemic (which killed around 1 million people) a guide for their estimates.
None of this is definitive (as they authors themselves say). But it does help highlight the magnitude of what we could— and likely are—facing.
See Coronavirus is highly uncertain and global costs could be high