Is there an obvious difference between cubic zirconium and a real diamond?

Go to a jewelry store. Put a cz and a diamond beside each other. You will see a difference. A cz clouds over time also. If you want better prices go to a pawn shop, seriously. I got my engagement ring there. Sure its used but the ring i got is sold in stores for $1000+ and i got it for $303. Just make sure you get them to diamond and gold test in front of you before purchasing. Down side you won't have insurance from them but can still get it insured elsewhere. And if possible find a pawn shop that allows refunds, but this is extremely hard to find.