Balsamic vinegar is one of my favorite ingredients. It is available in many different qualities or grades or vintages, if you will. The price for some of the better, aged vinegars go for some serious coin.
A lot goes into making aged balsamic. Here's the process:
while it ages and gradually evaporates, the liquid is transferred to successively smaller casks made of different woods, absorbing the flavour characteristics of each wood and becoming more concentrated with each transfer. Oak, mulberry, chestnut, cherry, juniper, ash, and acacia are the most commonly used woods
That explains why it is so expensive, costing $100 or more for a rather small bottle. A few years ago, we received a bottle as a gift. It was wonderful, but didn't last very long. Mario Batali tells the story that his grandmother received a bottle as a wedding gift, and used only a drop or two in very special dishes, so the bottle lasted many years.
But I found a trick. I buy 2 bottles of balsamic at Trader Joe's. This is pretty decent vinegar from Modena, aged 8 years. I then take both bottles and pour them in a little saucepan. Simmer until the vinegar reduces by half. Cool, and pour back into one bottle.
You now have vinegar that tastes very similar to the much more expensive tiny bottle of 30 year-old balsamic for about 10% of the price. And, because it is affordable, it can be enjoyed more than a drop at a time.