First of all tell me that this is an automatic system, so how can GMX will know that you will be charged less?
I'm not sure what you are asking or talking about. GMX is just an online exchanger which charges 12% fees to convert Evo into LR. That means you will get 88 LR for 1 Evo. But if you have used GET referral link, you will get 0.92 LR for 1 Evo.
BTW, one shocking news for all of us, I heard the news that the owner of the Evo is a scammer who was also owner of the scam altergold. Moreover, he is the owner of more than 200 HYIP and autosurf sites now which accept Evo wallet. I mean he has created those sites to promote his Evo wallet.