well, as a part of my spree from 2 weeks ago, I ordered knockoff cassettes from eBay.

Frenzy & Laserbeak from seller 1
- warped card, like most KO's.
+ full metal

Rumble & Buzzsaw from seller 2
+ mint card
+ full metal

when comparing to what S-O-C offers, the sheer wieght is noticable, but the cards aren't as clean. (slight bend, mushed spots, etc)