We can calculate the value of the phi function for the number $30^{90}$ as follows:
$\phi(30^{90})=\phi((2\cdot 5\cdot 3)^{90})=\phi(2^{90})\cdot \phi(5^{90})\cdot \phi(3^{90})=2^{89}\cdot(2-1)\cdot 5^{89}\cdot(5-1)\cdot 3^{89}\cdot(3-1)=2^{92}\cdot 5^{89}\cdot 3^{89}$
Can the same be done for $60^{90}$? When we broke down $30$ into prime factors, each of them was unique, whereas $60$ is different because there is another $2$. So the prime factors are not relatively prime to each other because $2$ is not relatively prime to $2$.