I don't pay for labor. Amusingly, an MBA student interviewed me about my tiny business, and could not wrap his head around the fact that I don't count labor in my cost of goods. I do have a rough estimate of profit, and of how many hours I work. The closest thing I could offer him was a ratio of these numbers, which is typically around $100 per hour. I make my widgets in my basement, and am usually able to take care of everything in one evening per week. It's the closest thing to passive income that I've been able to come up with so far.
I follow a rule that's common among micro-businesses, which is to waste zero time on disputes. I always offer a full refund right away, along with a boilerplate list of troubleshooting suggestions. In virtually every case, the customer comes back in a few days and agrees that my product works. But because of this, I consider a dispute to be an immediate loss, and not a dollar amount hanging in limbo.
If you shipped the product, you most certainly lost $100, plus whatever additional labor costs were involved in attempting resolution.
There's also the opportunity cost of having that cash illiquid, even if you do win the dispute in the end. Money's time is worth money.