A 1940 article in National Geographic reveals some of the incredible riches of princes in India. How did they maintain their wealth during the British Raj?
The British Raj was not monolithically in control across India. There were many princely states which continued to collect their own taxes and run their own affairs with only a small contribution to the exchequers of British India.
The rulers of these states could be extremely wealthy.
Here is a map of British India in 1947 showing the patchwork of quasi independent princely states (everything not blue or purple.)