eBay is also an excellent resource to find that rare, exclusive promotional figure too!  Occasionally, toy manufacturers will include a "secret" or "bonus" figure in a series.  Usually, these rare figures are only available by mail, at conventions, etc.

It usually works something like this:

Once you buy all of the figures from a particular series, you can send in "points" (usually UPC codes or coupons included in the packaging) to receive the bonus figure.  The problems with this marketing strategy, however, are many.  For one, the bonus figure sometimes sells out before a collector can obtain all the other figures.  Also, since these figures are usually limited to a smaller manufacture count, sometimes it's nearly impossible to find the bonus (or "premium") figure, even if you have purchased the others in the set/series.  Even if you do manage to track one of these hard-to-find items down, online & regular retail outlets specializing in "collectibles" often charge exorbitant prices for such exquisite finds!

However, eBay allows collectors & displayers to find these rare items much easier, and usually at a much lower cost.  For example, this "George Lucas" Stormtrooper figure, from the STAR WARS Saga line, is a premium figure.  In other words, once a collector has obtained four (4) other select figures from this series, he/she is eligible to receive this exclusive (providing of course, that it's still in stock and the buyer doesn't mind waiting up to 6-8 weeks for delivery!).

With eBay, however, an interested bidder/buyer can EASILY find such elusive goodies ... for example, this figure (below) could easily be purchased for roughly the same amount as one would pay in a retail outlet!