Bullshit.
>But then all those resulting weapons and tanks are being sent to Ukraine. They're not staying in the USA.
They don't need to stay in the USA. Most of those weapons systems are not even particularly relevant to the US' needs right now. Some are even literally expired, or near their expiration date.
The US has thousands of tanks and thousands of armored fighting vehicles stockpiled as well as thousands of MRAPs left over from various occupations in the Middle East. Not only do we not need more of them, but those weapons were designed, and built, primarily to counter a scenario in which Russia (/ USSR) invaded Europe. And that's now happening. They will be of very little use in the Pacific, and will be of no use whatsoever if they just sit in the desert for another 20 years.
So if you want to talk about opportunity costs, that should be part of the calculation.
> And all those extra workers that have been hired? Well, they came from working on other things. Things that aren't getting done anymore -- or the people that replaced some of them came from yet other things that now aren't getting done, that aren't benefiting people and businesses in the US.
Wrong. People, and jobs, are not 100% liquid. People doing manufacturing jobs can't immediately retrain to be software engineers. And I don't know if you've noticed, but there are a lot of people who worked in manufacturing struggling to get by in an economy that has globalized manufacturing out of the US.
You may have also heard that the US is now trying to get repatriate some of that critical manufacturing back to the US. Defense spending is a good way to keep those skills and supply chains viable.
> So no, there's no reasonable sense in which the money is "staying in the USA", in the sense of having our cake and eating it too. It's being spent on hardware that is sent to Ukraine. And we are losing out on all of the products and services that we would have built instead. All of that value is gone. Because it got shipped to Ukraine instead.
Since you're so interested in opportunity costs, how about we have a discussion about the opportunity costs of allowing Russia to successfully invade their neighbors? The political opportunity costs of failing to help a nation which we had strongarmed into giving up their nuclear weapons in the 1990s, and the subsequent risk of increased nuclear proliferation? The opportunity costs of dealing with the situation now rather than later, with more land and population at their disposal (1938 Czechoslovakia says hello)?
This is a rare occurrence of a scenario where it is in our interests to help Ukraine, while being the moral thing to do, while also being an insanely efficient use of resources comparatively speaking. Certainly far moreso than the 20 years spent in the middle east.