Instead of charging a fixed transaction fee for clearing the rights, Corbis tries to buy low and sell high, capturing the spread as revenue.

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Assuming that Amazon charges a fixed percentage of the sale price as its fee for every transaction, the service has the potential to generate millions, perhaps billions, in sales.

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When a credit card users make a purchase using his or her card, the merchant is charged a transaction fee by its bank that typically includes a fixed charge plus a percentage of the amount charged.

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