To calculate the GDP per capita, you can use the formula:
\[ \text{GDP per capita} = \frac{\text{GDP}}{\text{Population}} \]
In this case, the GDP is $25 million (which can also be written as 25,000,000 dollars) and the population is 500 citizens.
Now, we can perform the calculation:
\[ \text{GDP per capita} = \frac{25,000,000}{500} = 50,000 \]
Therefore, the GDP per capita for the tiny island country is $50,000.