HH are powerful, sure. But I think it's the novelty and rarity that makes them popular, important and worth selling.

If HC were that rare, people would sell them for money.

You see it in other games, too. Even items that bare no game-impact become worth real cash.

It's the culture of the game, and while evony cannot moderate what they cannot see, they also cannot be blamed for that which is a product of the culture.