I think in a lot of cases, you're right SB. But, I've had some truly spectacular smokes from very, very old tobaccos. The 1940s era Three Nuns was not the oldest. I confess, I've never paid big money for old tins, but mostly because I'm just not in a position to do so, and because I've been squirreling away vintage tobaccos since long before it was trendy to do so. Thanks to early experiences, thanks to my mentor, Robert Rex, I've always put things away to smoke in the years to come. I've still got quite a few tins from the 70s and early 80s, often bought at a discount because they'd accumulated too much shop dust. Once in a while, I'm disappointed when I open one, but more often, there's something really wonderful in those tins.
In some ways, I think it's a matter of expectations. When I open an ancient tin of Garfinkel's Orient Express #11, which many know to be pretty much my grail mixture, I don't anticipate a big latakia hit, but a softer, more complex experience, and it almost always delivers. When I want "big lat," I go for newer tins. I don't smoke these old gems as daily fare, but really appreciate them when I do.
Once in a while, when I open the last tin of something I've had in the "cellar" for years, I think about hitting the web to see if I can find a replacement. Then I realize I've got to pay the mortgage, my kid's school tuition, and put some food on the table, and just enjoy the fruits of foresight that Robert taught me. Still, I'm often more than a little envious of those who do manage to acquire these things. (Fortunately, I've got friends who share.

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Is $500 too much for a tin of something rare? Probably. At about $20 a bowl, it seems pretty steep. Then again, some people routinely pay more than that for a "luxury" cigar.
Some tobaccos do have a limited life span. Others seem to go on forever. Was that old Three Nuns great because it was old, because it was made differently in the forties, or because I dreamt into the experience a whole mess-o-expecations that tuned my perceptions to render something special in my consciousness? Probably a little of all three. That's okay with me.
And, I do often consider the economic foolishness of smoking these old tins instead of making a sizable profit from them. Then, I revel in another puff, and it all makes sense.