I'll add something else.
While I aim to discourage refund requests, I am also always open to accommodate customers, and how I go about it usually depends on how they approach me. If they come to me with a self-entitled attitude, I dig my heels in.
If, however, they make a genuine mistake and ask nicely, I give my best to accommodate them.
Sometimes this opens an opportunity to upsell them with a discount coupon for another product.
Just yesterday, I had an older customer who purchased one of my drum plugins, not realizing that MIDI loops were not included, and was wondering if he could get a refund because he thought the plugin would be useless to him. Normally, I would decline them and point to the loops they can purchase separately, but since this gentleman was on a tight budget, I declined the refund but gave him a comprehensive MIDI pack for free.
He got a great deal, and I got the keep the sale and the customer.
Our saying is "customer is not always wrong." π