Just refund them
I promise, it's not worth the hassle to fight it
Just refund them.
When you have a disgruntled customer, process the refund and move on with your life.
Yes, it sucks.
Yes, you did lots of work and incurred lots of cost.
Yes, it's "not fair".
But you should still just refund them and move on, for two reasons:
Resolving this is going to consume a bunch of your time. The customer is going to be annoyed and will argue with you about why you chose to refund $x rather than $y, and you'll feel compelled to engage. It's probably cheaper to just give them what they want and move on.
And fighting them on it will just create a superdetractor—a detractor who will gleefully post on social media and review sites about how awful you are, which will probably cost you more than the refund would have.
Every time I've broken this rule, I've come to regret it.
There are only two exceptions:
I don't refund more than the amount you paid me, and
If you were so aggrieved that you require a full refund, we also need to stop working together. The meal can't be so awful that you want all your money back but also want to eat the next course.
Totally agree