Level 7 PVP rewards includes, for ranks 101-200, a specific 2 star cover and 2000 ISO. For ranks 201-300, it’s 2 elite tokens and 2000 ISO. In other words, at a minimimum the lower ranked players get 2 2s, instead of one, and have the possibility of up to 2 3s instead.
Why is the lower rank geting better rewards?
I intentionally placed lower in the last pvp so I could get 2 elite tokens instead of a useless guaranteed 
Ended up getting 2x
out of it too.
This listed ranking doesn’t include the elite tokens you get.
26-50 - 2x 3* + 2x Elite (edited to add as I got this in sticks and stones)
51-100 - 2x 2* + 3x Elite
101-200 get 2* + 3x Elite
201-300 get just 2x Elite
This from CL rewards preview thread, I assume is still the case and not fixed yet:
[quote=“David [Hi-Fi]
Moore”]
Please note: There is a known issue where in-game (and in the screens below) additional rewards are not displayed. This will be fixed for events in the future. We’re working on a few charts today that show the additional rewards and will add them here when they are ready.
[/quote]
[/quote]
I can confirm that this is correct, as I got it in the Iron Fist PvP.
Thanks - updated my post
Would be nice if a community relations poster would come on with a handy table showing all this…
Yep. I placed in the top 100 of IF PvP event and got a 2* cover (Ares?) and three elite tokens. Even better, all three elite tokens gave me 3* covers…
It seems not to be the case everywhere - just ranked T50 in Sticks and Stones CL5 .. only to get two Moonstones/HP/ISO while T100 got two Elite tokens 
Though you do get an extra 25HP which in the devs mind is worth something. But no shot at a 3* does suck, especially when the 2* is Moonstone!
Again a nice table for rewards at all CL would be pretty easy to do…
[/quote]
Aha! Thanks for the info.
A better question is why, at scl 7, do you need to place top 50 to even get a 3* cover from placement?