I was exaggerating to make a point, it doesn't have to be 20, it can be one or two, if I own the copyright, I feel I should receive something for the extra copies. There was a thread going on yesterday about who owns the copyright to an application made by a hired consultant, I don't know if a conclussion was reached there.

And, yes, service contracts are important here and if you can get them to sign at least a 1 year contract, then maybe it'd be ok to install the application for free.

I'll try to rephrase my cuestion then, to you and everyone else reading:

Is it common practice to charge for extra copies to someone who has payed for the original development?, if not, why? just as a good bussines practice or is it plain out unethical?