The price of granite is determined by many factors. Where the granite is quarried affects the price.
Some granite is quarried out of mountains, off of the ocean floor, and in very remote locations.
Shipping from different countries has different cost associated with them also. Some quarries that are new have significant start up cost which is then translated into the price. In the more exotic types of granite, they usually do not have a large reserve. Since this would make the stone harder to come by it then drives the price up. Labor cost associated with different countries, along with the exchange rate on monies would also be associated with the price differences. The quality of the granite would affect the price. Some have fissures, cracks, or fill areas. Many of the exotics commonly have fill, but the extent of that fill could affect the price. As a buyer we always look for a good price, but keep this in mind, if it is cheap granite, there is usually a reason.