No Voldemort has not trapped Harry in a tiny cage. But the people who sell the movies have made a very smart decision.
On December 29th 2011 the Harry Potter films will be locked in a vault, to be re-released at the discretion of the studio. So if your family wants to own those movies you have about 7 weeks to find a deal.
Some of them are on sale if you want to grab a great deal now:
Harry Potter (The Complete Collection: Seasons 1-7) Blu-Ray $81.00 (Pre-Order Price Guarantee)
Harry Potter (The Complete Collection: Seasons 1-7) DVD $48.99 (Pre-Order Price Guarantee)
Or if you are just missing one or two check out the large selection on Amazon!
As always this is Amazon- they can change the prices at any time!