Hi Unipol,
I think that is a perfectly legitimate question to ask. I have asked that question myself. If I have seen an item change hands several times, I would particularly want to know why. Is it any good? Then why are you selling? What are its limitations? Perfectly reasonable questions, if one is showing 'due diligence' before making a purchase. Of course, the answer comes down to whether the seller is honest about it.
Fortunately, I have found most people on IIS to be honest anyway, but then, this is a small community and anyone who isn't are soon found out, as we have seen on a few occasions in the past.
There are all sorts of reasons why people sell 'stuff', usually to buy more 'stuff', although I mostly buy and don't usually sell.

Or maybe it is because I swapped my wife for a credit card and don't have someone nagging me to get rid of 'stuff'.
I sure am much better off financially, as I don't spend as much as she did! I certainly wouldn't have the scopes I have if was still married. Nahh, I would still be paying a bloody big mortgage instead.

Now I am debt free, at least, until I buy my new mount (EQ6 GT) on Tuesday, if it arrives.
Cheers Peter