If it installs on your HW and then activates properly on your machine online in the "Genuine Windows" test (or whatever they call it), then *it is* legit! At least according to Microsoft themselves apparently, and they are quite picky about this and they can easily kill/blacklist serials to prevent activation of foul copies. IMHO price is irrelevant to this.
Of course not. For example, if you somehow obtain a non-profit license for Windows (which is available at a dramatically reduced cost) and are able to install and activate it, do you think if Microsoft came knocking on your door they would consider you legitimally licensed? Of course not.
Most people don't care - they only care if they can install and activate. Doesn't mean you are legitimately licensed however. Microsoft is absolutely NOT picky - it's very rare that they will blacklist install codes - they only do it in extreme cases.
