I'm personally of mixed feelings about this. There are a few factors people seem to forget - like shipping, sales taxes (where applicable), and PP fees. I'm not sure if you are talking about any specific thing in the classifieds or the common practice of some people getting an item and selling it for quite a bit more than they paid for it. If the seller is covering PP fees and shipping, plus paid for shipping and maybe even sales taxes to receive the item to begin with, then their costs might be higher than you've allowed for.
And, some items really are rare or collectible so can fairly command an inflated price. For instance (I'm not planning on doing this, but if I was I could),---> I got a VV REO Woodville. There was a lot of demand for these, and just judging by the pressure on REOs webhost plus the fact they sold out in about 2 hours, I doubt that everyone who wanted one was able to get one. Over the next few days, there will be many, many posts singing the praises of this device. The VV Grands won't be out for at least another 5 weeks, so let's say I decide to sell my VV Woodville (Again, I'm not actually planning on it. This is just for the purpose of discussion). What's a fair price? I paid $212.05 for it shipped. I also had to change my schedule a bit and take a couple of hours off work to wait around to sign for the package, so I could sure think a couple of hours wages are part of the deal. Would listing it at $230 shipped be somehow unfair? $250? $275? (I do think I could get that much) At what point above what I actually paid do I become a profiteer or a jerk for selling it?
But then, I have seen a few times that people will snap up as many of a limited stock item as they can get knowing that there is limited stock and as soon as the vendors are sold out and people are singing the praises of that item on the forums, they'll sell what they bought for as much as double plus shipping. - I'm still of mixed feelings about that, but it does seem to be pretty obvious profiteering. If someone buys it - did they want it bad enough to pay double? Or were they just uninformed? Tough to say.