10k per year is only 'poor' in the US replace that with 1,000$ in 2012 dollars per year and you might have an idea where India considers the poverty line.
Basic food costs, which is most of what we're talking about, don't actually vary that much (if anything, they tend to be cheaper in the developed world due to subsidies). It's true that Indian poor pay much less in rent and clothing. But food makes up the bulk of what they have to buy each day, and they don't get a meaningful discount (beyond assistance programs like the one described in the linked article).
I don't have any statistics on this, but your statement does not match my observations. Even within the US, the exact same product in a Kentucky supermarket will often cost twice as much in a California supermarket. I shop in both and my food costs are dramatically lower in KY.
In Central America, I found local food prices to be highly correlated with affluence. Food (both served and in markets) in Costa Rica is significantly more expensive than just north in Nicaragua. Rural Panama is a lot cheaper than Panama City. Honduras is generally expensive; Guatemala is generally cheap; but there are zones of relative expense within those countries. Food in general is dramatically cheaper south of the US border, especially if you shop in public markets.
I have not been to India but I am told by friends that food prices are significantly below US prices.
Yes, basically, the only economic exchange at that point is bulk cheap food and that's at close to the same exchange rates. The real differences is how it's almost hard to be that poor in the US, even though so many people are that poor in India.
PS: There are places where houses sell for less than 1,000$ in the US.
