This is so sad. I am not here for either party to this issue, but with 29 years in the industry, I have seen this type of damage time and time again, and I tell every one of my customers, "do not lock down the back straps". Invariably, someone is going to come along, flip open the cover, step into the water and push the cover back and off of the spa.
Ooops, when they forget to unlock the back strap, and they push that cover back; excessive stress is applied to the locked strap, resulting in damage that looks exactly like this. Call it; "stitched close to the edge of the material" if you may, but stress takes its toll, and rips and tears occur. Imagine that.
Unfortunately, money is important to all of us, as well as, the two parties involved. On one hand, you have the owner of a new cover, implying, "I didn't do that, it just happened", in spite of the frayed material, and the maker of the cover saying, "Why is it my fault".
Except here, they both become losers; one with self inflicted damage that should be someone else's fault, and the other, suffering the fault of selling to consumers, especially when they want to inflict pain associated with their loss that should be someone else's responsibility, like under the "warranty" covering materials and workmanship.
There are reasons, covers cost different amounts of money, going from $300 to $500. They differ in grades of quality and mil thickness of materials, double stitching, reinforcements, double heat seal wraps, and the list goes on, but the price goes up.
When you buy on price, you typically get what you are paying for, making you not the “wiser one”, but the more frugal one.
My customers may choose to buy off the internet, and you know it when you see the cover as you approach. This is only because we know the differences, while the consumer sees only the price.
We, as Dealers, can only apologize for the quality standards in what we deliver, when the cost is more. Those who buy, either or, soon learn the difference, and then buy the next one from the dealer they trust.