Thanks in advance!
Millett and Snyder-Beattie's (2017) 'Existential Risk and Cost-Effective Biosecurity' is good for back of the envelope calculations on GCBRs: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5576214/
I can't be sure this is the paper I'm remembering but it looks pretty good - Bernstein et al. (2022) find that activities to prevent zoonotic pandemics save lives for a cost roughly comparable to top Givewell charities (I get this from their claim of saving lives at less than 1/20th of the low-end of the value of a statistical life, which they say is ~$107,000 - though beware unequal application of rigour). This estimate does not include economic losses due to a pandemic. https://www.science.org/doi/full/10.1126/sciadv.abl4183
And more indirectly, if you wanted to make your own back-of-the-envelopes, Marani et al. (2021) provide a well grounded probability estimate to work with (though the historical record would not be reliable for emerging risks from biotechnology): https://www.pnas.org/doi/10.1073/pnas.2105482118