Your bank spread is eating a quarter of your export margin

You realise export proceeds at the buying rate and buy freight at the selling rate. Using one rate for both hides a real cost that lands entirely on your margin.

Two rates, not one

When your export proceeds arrive, the bank buys the foreign currency from you at the buying rate. When you pay an ocean freight invoice in dollars, the bank sells it to you at the selling rate. The gap is the spread, and on Indian bank card rates it is commonly ₹2 to ₹6 per dollar.

A spreadsheet using a single mid rate for both sides silently pockets that spread as phantom margin. On a USD 40,000 shipment with a ₹4 spread, that is ₹1,60,000 of margin that does not exist.

What to do instead

Carry two rates through the whole build-up. Convert your rupee costs to dollars at the buying rate, because that is what you will actually realise. Cost your dollar-denominated freight at the selling rate, because that is what you will actually pay.

Then check the quote at ±5% on the rate before you set a validity period. If it stops being profitable at −2%, either shorten the validity or hedge.