Supply < Demand isn't greed. All the relic crafting mats being sold for far more than it cost to make (millions) isn't greed, it's poor design. Blame SE for the poor system sure, because with how it is, you are well within your right to, but don't blame players who see an opportunity, calling them greedy. It's not greed, these houses are valuable, they are worth money, people will buy them. Yes, thats a bad system, but that's not the fault of the budding moneymaker.
Also, the house is worth 60mil if someone is willing to pay 60mil, which in the current housing market is very likely, welcome to economy folks.
TLDR: Blame square, nobody else