Why is the Black Knight and the remaining knight skins in Fortnite so rare and expensive to buy?

I wanted to ask why the Black Knight or genrell of this Season 2 skins are rare. I thank you in advance and hope someone can explain it to me.

Because the Battle Pass are skins. So you could only earn them in Season 2. And since there were only a few players compared to today in Season 2, the skin is very rare

Thank you and how much is such a Fortnite black knight season 2 account worth about?

I think that is sold from 150 euro on Ebay.

But you should know that you can't actually sell your accounts, according to Epic Games. In most cases, nothing happens

Thank you so much, I just wanted to know what it's worth and why everyone celebrates it so much