Do you have any scientific evidences for that claim, because I have seen similar claims from SS Africa.
China did census and statistics with scientific methods countrywide for various subjects (population, quantity of rices produced every year, quantity of gold stocked in government storage, etc.) since perhaps before Qin Shi huangdi (200 BC), and they recorded statistics data very well in their books, which are still available today, so scientists can estimate relatively correct GDP data for 2000 years or 500 years ago.
Aside from China, no country did that, including Europe, until around 17 - 18 century.
India might be rich in the past in the sense that it had a lot of gold, but certainly no one can confirm and compare. European conquerors saying that "oh India was so rich" does not automatically mean India was actually rich. The same that European colonizers claiming Saigon was "The Pearl of the Far East", which delusional Southern Vietnamese still echoing today, but it was actually a city full of slums, dirty and relatively poor compared to even Khabarovsk (Russian Far East) or Nanning (a Chinese backward city in Quangxi province), Kuala Lumpur or Bangkok, let alone Tokyo, Shanghai or Singapore at that time.