I've always wondered that myself. Maybe it's ok with toys because you just play with/display them at home, whereas shoes you wear in public (Gasp! Fashion faux pas!)...or maybe if you played hoops in fakes it could do some serious damage Depends on the "primary function" of said Transformers shoe KO of the Prime/Megs Nike Frees: "It's all good!" KO of the recent Nike basketball shoes that came in the G1 box: "Kill! Kill! Kill!"
I have some of the KO combiners. The quality is pretty poor, but I doubt I'll ever be able to get an original set of any of them (with the exception of the RID repaint: Ruination). I'm also eying the Oversized Robot Master Optimus Prime, and the Robot Master Star Saber and Victory Leo set with a brainmaster! The KOs will never replace the original for me, but it's a good replacement, and when it's different from the original, I'm interested
