The explanation for the correct answer is that the total cost of the resort is 2,000,000 euros. The question states that Alpha invested 1,000,000 euros, Beta invested 500,000 euros, and Gamma invested an unknown amount. It is also mentioned that the investment of Alpha is one-third of the investment of Gamma. Therefore, we can calculate that Gamma's investment is 3 times the investment of Alpha, which is 3 * 1,000,000 = 3,000,000 euros. Since the total investment is 2,000,000 euros, it is not possible for the resort to be worth that much.