It's a pity they haven't announced the what's next after BoTG, which was the main way players earned $GODS.

The way I see it, rewards cards selling at cheap prices because they are easily minted or earned but some of it cost you more due to its usefulness while some were due to rebalancing updates that changes the current meta.

It's actually really dependent on your luck when opening expansion packs. If you got something like a Diamond quality Finnian (which is attainable with the expansion packs you get every week from Weekend Ranked), that would fetch you probably near to 1 ETH. And the great thing about GU is that everyone has the same chance to unpack one when opening a pack. :D