How much more wealthier was the avg Indian compared to the avg Englishman before the colonial era?
Secondly, Tharoor claims:
Ironically, Indian rulers in the past had largely funded their regimes not from taxing cultivators but from tapping into networks of trade, both regional and global.
This is remarkable. Did pre colonial Indian rulers really not depend on land revenue for their revenues?
The average Indian person was considerably poorer than the average English person prior to colonisation. It is difficult to know how much poorer exactly, but the available evidence from wages and GDP estimates suggests that Indian real wages were about half of English wages. (See Broadberry and Gupta, "The early modern great divergence: wages, prices and economic development in Europe and Asia,1500–1800" for wages, and Broadberry, Custodis and Gupta, Broadberry, Stephen & Custodis, Johann & Gupta, Bishnupriya, 2015. "India and the great divergence: An Anglo-Indian comparison of GDP per capita, 1600–1871" for GDP) You can put big error bars on the estimates, as there are a lot of shaky parts to the estimation, especially on the English wages side - Judy Stephenson has suggested these could be as much as 30% too high. But the basic conclusion that English workers earned more than Indian workers is not in any serious doubt.
Reasoning from the share of the global economy to the standard of living without first adjusting for population is just an elementary mistake. Monaco has a tiny share of the world economy, but does not follow that Monegasques are therefore poor. India has a large share of the world economy in 1700 because it was very large and densely populated. Its share declines over time not because Indians are getting notably poorer, but because Europe and the settler colonies are getting much, much richer, which is increasing the overall size of the world economy.