Case Trader

So maybe I'm missing something. I always bought 1 arena case for 25k honor at the Reward Vendor. But then, there is the Case Trader vendor, that let you sell/buy your cases for honor. When I browsed the list obviously there were no cases below 25k to buy and I said "lol who is so dumb to spend more, like 30-35k, for a case when he can buy the same for 25k from the official vendor?"
Then, yesterday, just for fun, I tried putting a case at 30k honor. And well someone actually bought it.

What's the explanation? Like, if you put case on case trader theres an higher chance it drops good items, and that's why people buy from there rather then from the official vendor?

I don't understand honestly :(

ignore case trader, that npc is there for the old honor system.