The IFR between 0.5-1% with 13.9% penetrance in NY, the worst hit area, is one of the worst pieces of news all around. It came out at the same time as the Geneva study and a study from late last month showing the same range for the IFR. This means it's 5-10x deadlier on a per-person basis than the flu, and will affect 8-10x more people.
Literally using these numbers, you can expect that going the "herd immunity" route would result in 2,000,000+ deaths (and that's without taking into account hospital surging that would occur if you did such).
It also shows that stay-at-home has been working, we have NOT reached these worst case scenarios because we have flattened the curve and prevented ourselves from being overwhelmed.
If you want to do the math yourself, just take 0.007 and multiply it by whatever area's population you are looking at, then multiply that by 0.85 (herd immunity for a disease that spreads this easily is about 85% of people) and you've got the likely number of minimum deaths from pursuing such a strategy, not counting hospital overwhelming effects of doing such.