Technically all 3x3 are knock offs of rubik's original design despite huge differences. At least that's my opinion. Right now most 4x4 and up are V-cube knock offs despite minor differences. They all took V-Cubes design and made slight changes to call it their own. And it makes me laugh that rubik's and V-cube refuse to change their design at all when slight modifications obviously make them soo much better. The biggest thing they could do, and simplest, is adjustable cores with screws and springs. Yes for 25+ years rubik's has released the same puzzle and been left behind compared to other manufactures and rely on their department store sales to keep them in business.
If Walmart could buy a large enough quantity of (insert intermediate speed cube here) and sell them in there stores for cheaper than rubik's. Who knows what would happen? some people would go for brand name, other would go for price, until people discover that cheaper one is better.