To understand the reason for the seemingly excessive cost involves an understanding and comparison of the production of Aceto Balsamico Tradizionale (lets call it ABT) compared to the production of balsamic vinegar (much cheaper and more easily found in stores all over New Zealand). It's important to note that the expensive ABT isn't really vinegar, as it's made from a reduction of cooked grape juice aged for a minimum of 12 years in a variety of wooden barrels by artisan producers in Modena or Reggio Emilia, Italy, who have been making this gorgeous condiment for generations. It has a pleasant sharpness, but it's nowhere near as sour as regular vinegar, and it also has a subtle, but powerful, sweetness and a thick syrupy texture. It's been mentioned in text from the Middle Ages - back as far as 1046 - so you're getting a lot of history with it.
Ordinary balsamic vinegar is made by mixing regular wine vinegar with colouring, caramels and occasionally thickeners to resemble the more expensive ABT. This doesn't mean it's a "bad" product, but explains why it can be made in enormous quantities on a daily basis.
The exceedingly more expensive ABT gives an enormous depth of flavour and a taste sensation not dissimilar to umami (the most recent of the tongue's senses as discovered by the Japanese). I have to say that the best way to justify the extra price is to simply no longer think of it as vinegar but as a rare seasoning. But of course, at the price you mention, who is going to take a risk on it - drizzling it on a charcoal-grilled steak, over buffalo mozzarella or on a tranche of steamed sea bass as I've had it over the years.
So, let's start at the beginning. Is there justification in charging $1200 for 300ml of vinegar? No. Is there justification in charging this same amount for a delicious ingredient that has taken 100 years to make, taking into account its heritage and strict production guidelines? Yes. I'd suggest you get a group of friends together and form a collective and buy a bottle. For 300ml, you'll have 60 teaspoons worth to play with. It might well be worth it.
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