In most industries, selling the same product twice is considered unacceptable. Not necessarily. There are a lot of businesses which sell you a service assumin

In most industries, selling the same product twice is considered unacceptable. Not necessarily. There are a lot of businesses which sell you a service assuming some "average" load. Web hostings, insurance companies for example. That's even before I start whinging about my monthly train ticket. But in pretty much any profession there's a chance of a promise not been met. If that happened I would expect an apology, and some kind of a remediation. For extra credit a small token of appreciation would also be nice.