The other city that may have a similar economy to Mecca is Jerusalem. This is because same as Mecca, it hosts an annual pilgrimage of a major religious group, Christians, which at that particular point bring in revenue. There are also visits by various tourists to the historical and Holy sites.
Mecca is a Holy Muslim city and is deemed the birth place of Prophet Mohammed. It hosts the annual muslim pilgrimage in which millions of Muslims from all over the world come to pray for a period of a week.