Most people on this forum do not promote used CPUs because of the inherent risk of used parts. I would never recommend used CPUs from non-certified online deals, and I wouldn't buy used parts like that unless they are from a family or close friend.
Inconsistency in used parts conditions and prices is not a valid comparison of worth across different CPU models.
Furthermore, you keep using the terms such as "better" and "destroys", which I understand the i5 is "better", but in specific goals, such as gaming, the Fx-6300 can reach solid 60 fps (depending on the GPU) in modern AAA titles. So how does this "better"ness translate to actual observable performance given specific tasks?