Difference in bumpers

[thejinx]

Trying to expand my knowledge. What are the differences between early, cross and late bumpers. If any. This question came to mind when I read somewhere that early bumpers are really expensive where crossvand late are not. Thank you

 

[Grazy]

I would have thought that crossover rear bumpers are more expensive as they are a one year only part
I also think the bumper irons are 72 only

Bumper prices seem to be all expensive lately