We have covered the topic of valuation in detail, several times.
I suggest you start by scanning the threads in the Domain Forum Library [webmasterworld.com].
Also, spend some time scanning backwards in time in this forum.
When it comes to valuing a website I'd say the leading value indicators are the quality of the content and the quality of the backlinks.
Search engine rank is vaporware. Defensible rank, based upon quality inbound links - the kind that can't be bought - that drive not only rank but traffic are a big factor.
For an ecom site the product doesn't matter unless its an exclusive deal. The product only matters in terms of the profit margin + strength of ranking factors.
You will find many folks argue for valuations based upon a multiple of revenue or profit. For example 1Xs or 1.5Xs etc.
Please note: The edit of your post conforms to the Charter. We avoid site specifics to deter people from posting what appears to be a question when it's really an "announcement" or ad.