I would have to consider several things before being disappointed in the strap. Such as: Is that the only issue? If not what are the others. What price case is this? Was the case expected to be better than you feel you got?
If it came from a custom case maker I'd want the strap replaced, which should be no big deal to do. If the case is a cheap import, I'd probable be satisfied and would feel I got what I paid for.
If I were selling the case I would explain, with pictures, the condition of the strap and any other issues the case may have. After all, isn't that what sellers are supposed to do? There is no such thing as giving too much info about a product that is being offered for sale.