All visitors to Comoros are required to have a visa. Nationals of any country can obtain a visa on arrival. Holders of diplomatic and service passports of China do not require a visa.
Based on the government website, visa fees are:
However, IATA listed the visa fees as US$50 or €30.
All visitors must hold a passport valid for 6 months.
References
Visa policy of the Comoros Wikipedia(Text) CC BY-SA