The difference between those guitars is.
The 2550 has a pickguard the 2570 don't.
The 2570 has shark inlays the 2550 don't
The 2570 has binding on the neck the 2550 don't.
But apart from that, it's the same.
The only thing that would be different between the JEM555 and the 2550 is,
The 555 has an American basswood body and the 2550 is just basswood.
The tremolo is different (I would say less good on the 555)
The pickups are different, both are Dimarzio ones but the ones in the 555 are more high output ones (less good in my taste, but not in Steve Vais taste, he likes them Evolution ones).
The inlays in the neck are different.
The placement of the input jack is different.
The JEM555 is not crap, just a little downscaled version of a more excessive JEM.