How would you charge such an app(s)?

>>Thanks Gerry for your response. I guess I have used wrong words. I have a small app for a retail store already made, but this company want so many such copies (meeting on Wednesday) and a main copy for their H.O. Internet won't play much of a roll just emailing zips at the end of the day.
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>In your case, when I was referring to "transactions", I was referring to "POS transactions". It's based on the concept of: Pay as you go.
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>Big customers pay more for the same software than smaller customers.