Hard call really, I guess it depends on how guilty you feel, because that is what it boils down to. How you feel about selling an item at a price greater than you paid for it.
I mean is it wrong if I pick up say a mountain bike, in good condition, at a garage sale for $50 and then place a for sale add in the local trader for $250. Or should I say to the original sellers, "look that bike is really worth $250, here you go" and give them $250. Or I go to an import auction in Brisbane and pick up a Ferrari for $5000, is it wrong to then onsell that Ferrari for $35000?
I don't believe it is morally wrong to buy an item at a bargain price and then sell it for a, (dirty filthy word) profit later. If both the original seller and the buyer are happy with the first price where is the problem.
Of course there is the flip side. The original seller sells at a reduced price. Later they find out how much the items resale value really is. They then contact you and ask for the difference between the original price and their new discovery price. Are you going to make up the difference. I don't think so. Besides I'll bet originally that the though "Jeez that's a fantastic price. Much cheaper than I've seen it anywhere else. Damned if I'm going to let that get away.

" has passed through many minds when a bargain is spotted.
I know I'm not speaking for everyone here, but hands up if this thought has crossed your mind when you've seen a bargain. Ever thought of contacting the seller and saying "Hey, you've got that way too cheap."
Guilt can work both way