Arriving Lowest landing cost in a Tender.

In a Global Tender what is the rate I have to load against International bidder who quoted a price stating that all Indian taxes are to the Purchaser's Account. The contract execution period may be about 3 years and the work includes Design&Engineering, Supply, civil works, erection, commissioning, performance guarantee demonstration and final acceptance by purchaser. The estimate is prepared by the purchaser is around Rs.500/- and he didn't anticipate any Indian income tax component of the bidders.