I think you posted in the wrong thread.
Did you mean to post in Ask HN: Did offering a money-back guarantee help your business? https://news.ycombinator.com/item?id=19085526
Did you mean to post in Ask HN: Did offering a money-back guarantee help your business? https://news.ycombinator.com/item?id=19085526
The counterpoint is, if your product genuinely is terrible, the cost of such a guarantee would be too high to bear.