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Yep. Buying razors as collectible investments is a huge risk. If the straight razor interest decreases again, your investment will tank.
And even if it doesn't, it may be hard to get cash short...

that's the other thing: buyer beware.
It is not impossible to find a NOS sheffield razor. I have had 1 John Barber that I am pretty sure was NOS.
But it is very rare. In those days, they were made...

NOS has absolutely nothing to do with 'value' as a shaver. After all, a razor shaves just as well if it has been used before.
It is mostly a factor regarding collectibility. And as someone already...