I don't know about you but I think every other would-be get-rich-quick-through-vintage merchant is doing the would-be purchaser a disservice.  The very word 'retro' suggests to me something that really ought to be dead and buried - or, at best, viewed with nostalgia - rather than as a living, breathing thing that is capable of evolving.  Once the very notion of 'Ivy League' is blurred by that of 'retro' (online sellers take note) the would-be purchaser is receiving very much the wrong message.  Doesn't help anyone, neither the buyer or the seller.  'One-off' might be a better way of putting it.  Even 'vintage' conjures up a certain mustiness.  Is 'deadstock' any better?  I wonder.  'Americana' or 'American clothing' can't quite cover it, either.
Worst of all is the dangle-the-bait-and-they'll swallow it-Ebay seller: Ben Sherman shirt: Mod/Skinhead/JohnSimons/retro/vintage/ska/Motown...  I exaggerate somewhat, but you'll have all seen it. 
I do love 'vintage' shops, though, don't you, with their rail after rail of RL, Tommy, Champion, bits and pieces of Timberland etc.  Maybe, every once in a blue moon, you'll turn up something.  But even the lowliest charity shop in an obscure back street might offer less predictability.

Just a few random observations.