10 fold over what? A problem since the beginning is that many people are confusing CFR and IFR. Worse is when people compare the IFR of COVID-19 to the CFR of the flu. Regardless, the IFR for COVID-19 has been thought to be .5-1% since the beginning. If we assume the NY antibody study is mostly correct (even with the sampling errors), I believe it puts the IFR in the .5-1% range [1]. If that IFR holds it still means 1.6-3.3M deaths in the US assuming the healthcare does not get overwhelmed.
[1]
deaths/(cases x 10 fold) x 100 == IFR
21908/(288313 x 10) x 100 == ~.75%
Data pulled from https://www.worldometers.info/coronavirus/country/us/ on 4/26/2020 @ 8am EST.
You cannot assume that 100% of people will be infected. Looking at case studies like USS Roosevelt (840 of 5000) and Diamond Princess (712 of 3,711) as the worst case prevalence because they are much higher-R environments.
So basically your IFR based fatality numbers could be divided by roughly 5.
There is some news out that is putting the IFR closer to .3% on the low end. That is great news if it holds up. The problem is that the numbers out of NY, if flawed would bring the IFR lower than reality, and they are ~.75% IFR.
Which is why when these studies happen, the public is told to wait for it to be assessed, rather than pretending all of us are remotely qualified to judge the content and draw conclusions from it about what actual risks the general population might be facing.
A good place to keep an eye on for the short term would be Sweden. Despite the lack of lockdown their disease penetrance is still on par with the UK.