How much profit it there in trading in MISB? You'll have to keep them for quite a while, if you buy them new. And if they are already some years old, aren't they very hard to find? Couldn't you make more money spending time doing a real job?
Don't get me wrong, I like trading on the net very much. But I trade in items that make a quite some money. 3-10 times what I payed for them.
Some of my playmo is still in the box. Sometimes because I have the set twice, sometimes because I don't need it and I keep it as a gift for a child or for bartering.