When I see the lowest fares on the India sites, some of the fares are restricted:
SALES_RESTRICTIONS : FARES MAY ONLY BE SOLD BY S2 OR 9W.
TICKETS MUST BE ISSUED ON EITHER THE PLATE OR STOCK OF
S2 OR 9W AND MAY ONLY BE SOLD IN INDIA.
OR - FARES MAY ONLY BE SOLD BY TRAVEL AGENTS.
TICKETS MAY ONLY BE SOLD IN INDIA.
Where the (higher) fares offered on the US sites are more expensive (ex. Rs. 3329 vs. $105) but don't carry this restriction.
Does buying from an Indian web site qualify as SOLD IN INDIA? I'm not sure what that means for an online purchase.