Let’s paper napkin this. A quick google search says there are 809 Million people in this world over 60. The death rate over 60 is roughly 10%. So if for the sake of the economy we just ignore it and let this sucker rip through the populace. Would you be OK with 80 Million extra people dying ober the next year?
Like a poster above, your math assumes that 100% of a certain demographic would contract this virus and do so immediately. That hasn't happened anywhere yet, and it's unlikely to happen in 12 months as you imply, even if no action were taken. That leads to sensationalism that's not really helpful.
Italy has a population of 60.8 million. About 21% of those people are 65+ for a total of 12.7 million old people according to wikipedia (I know). They've had a total (across all demographics) of 21157 cases and 1441 deaths according to the WHO's latest Situation Report from March 15:
https://www.who.int/emergencies/diseases/novel-coronavirus-2019/situation-reportsEven if all of those cases and deaths were in the 65+ demographic, that would mean that just .166% of the most vulnerable demographic has contracted COVID-19 in the 2 months that it's been known to be in Italy. Extrapolate that rate of infection for the global population over 60 that you gave (809 million), and you'd have 1.347 million cases globally. If you're correct, and 10% of those over 60 die after contracting COVID-19, then it would be 134,700 deaths globally which is an insane number of deaths, but it's a far cry from the 80 million that you estimated.
Also, Mean age of those who have died from COVID-19 in Italy is 81 years old, and 2/3 of those had underlying health issues such as diabetes, cancer, cardiovascular disease or a history of smoking:
https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30627-9/fulltextIt's not afun thought, but how much should be expended trying to save people with very little time left anyway? There's a decent chance that the economic impacts from these shutdowns will outlive a normal 80 year old with other health issues, even if that 80 year old doesn't contract COVID-19.