well for current value price guide i would look at ebay completed listings to get a rough idea.Of course condition,graded or not graded will affect price.I would also avoid the overpriced BIN you see.
A few i dug up
http://www.ebay.co.uk/itm/STAR-WARS-VINTAGE-KENNER-1984-POTF-COIN-LUKE-SKYWALKER-AS-STORMTROOPER-/191857505130?hash=item2cab99336a%3Ag%3ANQAAAOSw6kxXIShl&nma=true&si=owKWXbPTC4bJgJVbPXRIoXBa7hc%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
http://www.ebay.co.uk/itm/Vintage-1984-Star-Wars-POTF-Luke-Skywalker-Imperial-Stormtrooper-outfit-MOC-/322082190378?hash=item4afd98342a%3Ag%3A1ZkAAOSwiYFXGE3M&nma=true&si=owKWXbPTC4bJgJVbPXRIoXBa7hc%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
http://www.ebay.co.uk/itm/Vintage-Star-Wars-POTF-Luke-Stormtrooper-92-back-/121962018777?hash=item1c6580b7d9%3Ag%3ADfQAAOSwiYFXFkj5&nma=true&si=owKWXbPTC4bJgJVbPXRIoXBa7hc%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
http://www.ebay.co.uk/itm/Starwars-LUKE-SKYWALKER-Imperial-Stormtrooper-AFA-GRADED-92-BACK-POTF-/291714647248?hash=item43eb8c44d0%3Ag%3A3ZwAAOSwoudW7ya9&nma=true&si=owKWXbPTC4bJgJVbPXRIoXBa7hc%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
http://www.ebay.co.uk/itm/Luke-Skywalker-imperial-stormtrooper-outfit-POTF-carded-original-factory-sealed-/252358478250?hash=item3ac1bcc9aa%3Ag%3A4hYAAOSw2GlXE0S4&nma=true&si=owKWXbPTC4bJgJVbPXRIoXBa7hc%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557
chasing a clear bubble potf is like chasing a rainbow they have a very high probability of turning yellow then going brittle then bubbles cracking or splitting
As an alternative i would prefer a tri logo over a potf,no yellow bubbles to worry about.
http://www.ebay.co.uk/itm/Vintage-Star-Wars-Luke-Skywalker-Imperial-Stormtrooper-Outfit-Palitoy-Tri-Logo-/222083785111?hash=item33b539a197%3Ag%3Ak-EAAOSwZ8ZXDLQj&nma=true&si=owKWXbPTC4bJgJVbPXRIoXBa7hc%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557