Gold is expensive because there are limited quantities available. In addition, it is expensive to produce, which also drives up the overall cost.
Gold tends to be one of the most expensive metals on the market. The primary reason for this is because it is hard to find, and when it is found, it can be difficult to extract from the earth and produce into the desired form.
The price for gold is set on its demand. Because it has been used as a form of money throughout the history of society, it also varies based on economic conditions. Generally, when the U.S. dollar is considered weak within the economy, more people will invest in gold because they feel like it will always have significant value in the marketplace. This also drives up the price.