Or take true cinnamon, also called Ceylon cinnamon. It's sweeter and makes for better baking, which makes it a must-have for high-end bakeries and Mexican chefs, but you've probably never heard of it because it's not grown at the same scale as Chinese cinnamon (the kind you get in the supermarket). Grocery stores don't bother with these rare s**ces, due to the cost difference and limits on mass marketing. Think a grass-fed ground Angus burger versus a Big Mac -- everybody knows the former is better, but McDonald's moves a lot more of the latter.
But it's not all for people who wear ascots and refer to themselves as "gourmands." One of my colleagues in New York fields big tamarind orders from Buddhist groups, and he never knew why. One day he asked, and it turns out they use it to polish statues the old-fashioned way. There's also camphor, which makes smokeless gunpowder -- historic ammunition makers still ask for it, in order to make authentic duplicates. At least, that's what you assume when a guy dressed like a redcoat runs into your shop rattling a musket. It's probably best not to ask him too many questions.
Never challenge a man who willingly eats hardtack.