I see nothing wrong with it, although I would not appreciate someone buying and selling for the sole purpose of profiteering and having no interest in the item beyond that, or some excuse for doing so...
As far as selling something for more than you bought it, I have to admit that I myself have been guilty of that.
I bought a 17mm T4 off ebay and used it for several months before deciding it's not for me and I'd rather have the $$s than the EP. John (xstream) I hope will forgive me, because I sold the EP for just a few bucks under what I was willing to pay for it on ebay (my highest bid) and not the amount I actually paid, which was almost 10% less. I still would think it a good deal so I have no guilty conscience about it.
I've also had extra bits and pieces thrown in with overseas shipments, which I bought with the intention to resell unused to help cover the shipping costs. I soon found out that doing this is always more hassle than it's worth. (if you consider time spent advertising, packing and posting the goods, it works out that you are making less than the minimum wage.
)