Convert the complete purchase cost, not just the shelf tag. Include local tax, card foreign-exchange fees, baggage or shipping, and any warranty or return limitations.
Use a current rate with a timestamp, then compare the result with the delivered price at home for the same model. Exchange rates and bank fees can move, so treat the estimate as a range rather than a guaranteed saving. Check whether you can actually use the product in your home region.
Which two final prices are you comparing?