Interestingly, I had a US-GYE Basic Economy flight that I booked a few months ago and cancelled within 24 hours to get a main cabin fare. Used a $100.00 AA eGC + cash on it and my refund was the cash portion back to the card and a $90.00 eGC to replace the original. Decided it wasn't worth pursuing but this makes me wonder if there's more here as it was also exactly $10 shorted.