So in respect of the original thread title question, "How much of a premium are we talking for newsstand issues v/s direct editions?", the answer for me is it depends.
If a title has no collector interest it likely won't matter whether a newsstand version of a particular issue is 10 or 1,000 times scarcer than a direct. No one collects it, so the prices stay the same. You can pimp it all you like, no one will buy it.
If an issue has some collector interest / desirability, a premium may creep in if the newsstand version is comparatively scarce as collectors will see it as a limited variation on a desirable book. Collectors and speculators will always buy desirable books.
If an issue has rabid collector interest, and is for a character that attracts completists or run collectors, a newsstand may attract a huge premium if it is perceived to be extremely scarce (but not if it's an annual )
Finally, if a newsstand is in the possession of Chuck Rozanski, it will be priced x1,000 direct edition value regardless.
Well, that passed the time.
Yours sincerely,
Captain Obvious