The answer to the question of how much it would cost to buy an island varied according to the region and the method of purchase. The price of buying an island in the Caribbean can be very high because there are many wealthy real estate investors in these areas looking for investment and holiday spots. Similarly, buying an island in the United States also required consideration of geographical location, history, culture, and landscape. If one wanted to have permanent property rights and use it for military purposes, one would need to choose a suitable island according to the specific situation. Some islands may be prohibited from entering because they may have been used for military purposes or are under political or security threats. Under these circumstances, buying these islands can be very expensive because they need to go through complicated legal procedures and regulations. For example, islands of 100 square kilometers to 200 square kilometers could cost millions of dollars to tens of millions of dollars. However, it should be noted that these numbers are only estimates. The exact price depends on many factors such as geographical location, history, culture and landscape, market demand and supply, and so on. In addition, the purchase of these islands required detailed research and due diligence to ensure legal and sustainable investment.