FLG is correct - Aluminum cases are more expensive/popular because they dissapate heat better while looking good too
Copper Cases would be even more popular for thier heat dissapation if they were cases, however the metal is far too bendable and no where near the sturdiness people need in cases. I have a friend who uses Lian-Li almost exclusively for his builds. You can't be dissapointed with this case. Modders also use the case often as it provides a blank canvas of sorts to express there ideas.
Good Luck with it Tin,
-Joe