Star Wars: The Old Republic is that a lot of them are limited. Sure, you might be able to buy Revan's Mask, but you have to decide which of your characters will get to wear it. But that's changing in patch 2.1. A recent interview sheds more light on the upcoming Collections system, which will allow you to unlock items you have obtained on one character for repeated access.
Once you've obtained an item on a character, that item will be marked in your collection, allowing you to recreate that item for that character. Pay a few Cartel Coins and that item unlocks for every character in your account, including characters on other servers. The system will include mounts, armors, and pets, with more room for special promotions and the like in the future. So now you don't have to worry about who gets the special mount -- everyone can get the benefit.