A fair accounting of the costs would discount the items that are old and were going to be used somewhere else or scrapped if not used here, halving or possibly even decimating this estimate of direct costs.
That is direct costs, however. The indirect costs are astoundingly huge, as we all know.
There are a very small number of things I agree with r/Conservative on, but that this was a stupid war to start that America definitely isn't winning is one of them.