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But basically the key is testing and it comes down to the affiliate program's payout and conversions. If you can make one affiliate sale every 100 clicks that pays an average $36 commish vs getting 5 cents a click and only make $5 for the same 100 visitors then the affiliate program will earn you more. But some affiliate programs don't convert so you'd make more with AS. You really just need to test different merchants and different ad placement to see what earns the most.