Wiki doesn't agree:
http://en.wikipedia.org/wiki/British_Raj#Technological_and_e...
>India's per capita GDP decreased from $550 in 1700 to $520 by 1857, although it had increased to $618 by 1947
I'm not sure whose dollars those are... but it certainly doesn't sound like the Mughal empire ever controlled anything remotely approaching 30% of world GDP. Here's how the British won India, for reference:
http://en.wikipedia.org/wiki/Battle_of_Plassey
750 European soldiers and 2100 sepoys defeating 53000 Indians speaks volumes about the latter's ability to organize.