What the Fed is doing will work very well, at some modest real cost later on (likely to the dollar, represented in the cost of things we import and commodities), if we are able to somewhat restart the economy in the coming months (and we will). The worst of the NY region's situation (which is overwhelmingly the primary problem in the US) will end in the coming weeks (it's ending now, represented in the plunge in hospital and ICU admissions; the deaths will lag though). The Spring and Summer heat will dramatically reduce the virus transmission, combined with practical ongoing measures like heightened rapid testing, distancing and quarantining (along with occasional lockdowns that will spring up due to burst outbreaks; we will likely get far more aggressive with tracking people regarding outbreaks). There's a decent chance we'll combat the virus short term with a serum therapy (might be able to considerably reduce the per case mortality rate over the coming year), and then a vaccine is definite later on.

The tangible cost to what the Fed is doing, is that they will effectively destroy low single digit trillions of dollars in wealth held in US dollars (picture household wealth at $100 trillion for this purpose, and then picture the Fed lighting $1-3 trillion of that on fire as a means to prop up the economy; they're debasing our national wealth in this process, drawing on it via their control of the dollar, to point it as a firehose at the fire; not exact figures, merely a conceptual representation). That damage is likely to be anywhere from one to a few trillion dollars in real losses that they'll see from their programs (only a portion of what they do will result in losses of real value, as in the actions taken by the Fed during the great recession; % losses will be higher in this case, as they're doing some wider, riskier things). They're trading that hit as a cost to prop the whole thing up until the economy can find its legs again.

It's absolutely the right approach. It's the only serious option, other than doing nothing (which isn't reasonable, but it's another option). It will not be without a cost. It will prevent a far, far worse catastrophic outcome. If unemployment peaks at ~14-18% (it's almost guaranteed to hit at least the 15% area somewhere, and soon), without the Fed's actions you could easily double that figure.

The US is incredibly fortunate in this case. The many choices of our ancestors, which made the USD the global reserve currency post WW2, we're cashing in that rainy day benefit right now. We've been irresponsible with our fiscal condition the past 20 years, so our primary fiscal back-stop is the US dollar on such a short notice desperate need (this is far beyond the great recession, in terms of extreme sudden need of dollars); using that is a form of a tax against the assets held in dollars and the productive output of the US economy.

There is a very plausible scenario where the US dollar sees little negative impact despite the trillions of dollars in magic printing the Fed is going to do. And that is: the other major currencies it is competing with globally, are all supported by economies being similarly smashed right now (Eurozone, China, Japan; and the Chinese Yuan has very little global footprint, so it's not very relevant to that context presently, it's really mostly the Euro). The global demand for US dollars right now is extreme, which pushed the dollar to a very high level recently. That dollar demand, for liquidity purposes, will relax later on as some normalcy returns with eg a vaccine (within ~12-18 months sometime probably), and then the dollar will see some fallout from what the Fed is doing now, that's when the long-term cost will begin to be represented in such things as consumer prices, commodity prices (priced in dollars), and so on.

People with assets will benefit tremendously from what the Fed is doing. The stock market would be anywhere from 1/3 to 1/2 lower than it is right now, if the Fed hadn't stepped in in an extreme way (and I don't like where the market is at right now at all, it's not properly pricing in the grinding damage we have to deal with over the coming year, it's temporarily buoyant on the Fed's sugar actions). This is the world's largest bailout for asset holders, and it also happens to be very necessary to preserve the economy until it can return to functioning properly.

The only approach that would have maybe been better, is if a national hold had been placed on all major firings, all mortgages and rents for N months (3 months initially). The Fed would then step in to pay that toll directly (ie prevent the fire, rather than try to put it out afterward), along with the Treasury doing various programs. That could have possibly prevented more damage than what we're doing now. The US system, legally speaking, doesn't allow for that kind of command-economy type action very easily though. So the Fed's moves, which were 'guns at-ready' and made possible by the great recession, were the best choice we had (if this were 2007 and it were happening then, the Fed wouldn't have been able to move as quickly; there was a lot of stumbling around in dark in the initialy days of the great recession, trying to figure out what the Fed was allowed to do and what made sense).

Long story short, the Fed is eating some of our national wealth to do what it's doing, that's the tax we're paying (and some of that is being paid by the rest of the world, as the dollar is the reserve currency and widely held). Instead of everyone selling off 1-3% of their wealth and handing that cash to a central authority to take bold actions, the Fed is doing a conceptually similar thing via 'stealth taxation' (aka inflation (which won't register near-term due to very slack demand), aka dollar debasement, aka printing).