I'm o.k. if certain products from an LE collection sell out after a couple of weeks. After all, that is what LE is all about. If stuff hangs around too much, nobody will feel the urge to buy it and eventually lose interest. I assume that some items are easier to produce again, so eventually they show up. I was surprised to see STO coming back again. Where did MAC dig out the melted gold, muaahhh.
As for paying 50 bucks for an item on ebay (I assume to a product that was not more than $22 at regular retail price), I just stay away from it. I bid on ebay up to a certain point, but then I just led it go. After all, it's just make up.
I still wish MAC would make available larger quantities of the "hot" products. But who knows, maybe they do and somebody (e)buys them all in one go.