.. His time is obviously worth money, and that is easily quantifiable (hence the labour cost is often separated from the parts cost). His skills cannot easily be quantified though, and (similarly to software development), the cost has been invested already, so there's no marginal cost involved. Your example here equates to someone expecting you to write a program for free, rather than someone feeling they have the right to take a copy of a program you've already written. Again though, I'm not trying to claim that either of these are in any way justified.