Re-Roll on Loot

So i'm not sure if this has been talked about somewhere else on the boards and if it has i apologize for asking again, but was hoping someone from Riot could maybe answer my question. Last night i got a bunch of chests opened and after having a fair amount of skin shards i didn't know plan cashing in, I decided to give my luck a try and re-roll some skin shards into permanents.

I decided to take 3 of the higher value skin shards (surprise party amumu, celestine soraka, and dragonslayer panth), all of which i knew where higher value cause you are told when clicking on them. I thought because of this I would be assured a skin that was of similar value to the other 1350 skins. After the re-roll i was granted 100 orange essence and ruthless pantheon skin permanent. Is there no guideline for how much value these skin shards are worth when re-rolling?

I know I don't have too much room to complain as it is new content and whatnot, but had I known I would only receive a skin worth 520 I wouldn't have rerolled them in that moment. Just wanted some more clarification with the system, I really appreciate what Riot is trying to do, but I still feel like I lost out in the long run with what I got for what i turned in.