See, I don't really get how 5 million is really *that* big a deterent. I mean, unless they just buy it off the RMAH, it takes 3 Radiant Star Gems PLUS 20 mill gold PLUS 10 Demonic Essences. Players who can afford that can probably afford that 5 million for the limited occasion changing (which is what replacing a Nat's Chest with a better one probably would be). However, they probably can't afford to do it how Blizz doesn't want them too - build one and just pass it around their characters.
Of course, those people buying and selling items in the 1E9+ gold range probably don't care about a piddly little 5 mil, but they can probably afford to make more than one in that case.