Gaffer Tape said:

However, if you're genuinely buying it used, as in buying it from someone who originally bought it and then decided to no longer have it, then that's a different story. You're not creating any more demand the product. You're simply creating a situation wherein one unique copy is being effectively shared between two or more people, when it would previously have only been meant for one.

Except you ARE still lowering supply. If you buy it, someone else can't. It doesn't have the same effect that buying it new would, but it will still have some effect. You're increasing the "final destinations" for the BD by 1.

But wouldn't that even out? The person you're buying it from lowered the supply by one.

It depends on whether they'd sell it to anyone but you. If you are the only potential buyer, then it doesn't really make a difference. But if they might have sold it to someone else- now they can't and that person will look elsewhere to also give it a permanent home.

On the other hand... if this person is only selling to you... and they know you'll pay them for it when they've "used it", then that might have encouraged them to make a purchase they wouldn't have otherwise made- knowing that they'll eventually resell it to you. So, yes, two people used it instead of one, but the purchase was ultimately still made with your money.

These movies are perhaps different in a key way when compared to most other disposable entertainment. People putting $80+ down on the set are not as likely to watch it once and then try to offload it on the next victim (as most, say, video games). People are generally buying these to put on their shelves for all time. Because, Hey! It's Star Wars. On Blu Ray.