Although it is headquartered in Switzerland it is a fully international organization and completely free from any particular national curriculum. However, it is worth mentioning that all IB schools in India are not that expensive as assumed by the majority. There are a number of IB schools in India with a school fee structure of around Rs. 35k to Rs. 60k per month. In some cities like Indore, the school fee structure can be as low as Rs. 10k per month in cities.
The school fee structure can go up to 8-10 lacs per annum but that is the higher end in big cities like Mumbai, Delhi, Bangalore, and such a school fee structure is mostly for affluent areas with world-class infrastructure even these cities can offer something much lesser than this with lower fee structure. You can read more about IB tuition fees at this blog: https://tychr.com/are-ib-schools-really-expensive/