I don't agree. If things go badly, after an ugly settling out period, trade will resume. If I want you to do some carpentry for me, and I have vegetables, you may not want enough zucchini to feed an army in return for your week of labor. If other people value silver, you might want the coins I got from 50 people in return for that zucchini, since it is much easier to carry and doesn't spoil. You can then trade a little silver for beef jerky, a little for flour, a little for cheese, etc.
All that junk silver will jump start a transition from barter to a trade economy and help us move out of a Mad Max world or whatever happens in an economic collapse. Gold and silver coins are scarce, and they carry real value if people see them as a convenient way of symbolizing the value of the goods or services they were traded for. Coins as money worked from 3,700 years ago to 100 years ago just like paper money today (but inflation-proof if they are not shaved down or diluted with a higher proportion of base metal).
