Profit margin for an item like this overtime increases. As it only costs the company once to make the application. Money for programming and testing, possible marketing. Then it's put up for sale on a virtual store (non brick and mortar, like the Apple Store).
As you sell more and more of this kind of product, eventually you recover the costs to make it, then it's pure profit. Just like a music you buy digitally. The costs are hard defined. Then it sells over and over and over again, no overhead to very little.
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