For my earnings today, i have 600 dec and i rented cards with a total of 15k power and 523 DEC.
I'm grinding in Silver III and every win, i earned 12-14 DEC per win which is kinda fair. I started at 100% ECR and stopped at 50% ECR.
My total DEC now is 800 DEC which is 200 DEC profit and not bad for a newbie like me.