It seems the gills are flared on the DOA pics. Could it have been an oxygen shortage? Was the water milky, indicating fouling from ammonia? Water temp upon arrival? Just guessing but jeez, a four hour flight, I just kept over 100 fish (some quite large) in bags for 30 hours while traveling-WITHOUT OXYGEN, without water changes and no losses.
I think this catfish species evolved in extremely highly oxygenated water and if so, shipping any larger specimen would be a challenge for an expert.
If any seller commits to LAG or refund and does not follow thru after procedures are documentably followed, all intermediaries profiting from the listing or transaction owes it to everyone to investigate, validate facts, then when complete: report findings and if justified: take actions and keep the confidence of their customers. Anything else is just taking $ without earning it. There's a word for that. right?
That paypal did EXACTLY THAT and bailed on their responsibility is nothing new. They are/were owned by eBay, the masters of eluding responsibility in dispute management, but at least they predictably side with buyers.
Not throwing stones either way, I deal professionally in livestock and can assure you, I've lost more $$$ in losses than most individuals due to risky purchases and genetic manipulation but as said in the movie Goin' South, "them's the breaks!". When I make 1500$ on one animal, it helps fill the valleys too. Livestock IS risk and one mantra to remember-"they'll all die sometime".
Appeal to the intermediaries again, report their level of cooperation where a google search will let the world know and if necessary, get a collection agency. I've heard outrageous percentages charged as fees, but the satisfaction of knowing they'll be ...ummmm...amazingly persistent is worth a few bucks too, especially if your best efforts lack success.
I know neither of these parties nor have ever completed a deal with them.