For those who want to get upgrade cards out of their deck.
You can, for a small cost, send an Upgrade Card to your Dead Deck. But, here's the rub: If you ever wish to return the card to your deck you must pay 10%-25% of the cards value. And that just returns it into the mix. And to actually get that upgrade, you'll have to pay the regular price.
(Infinite Cards like Energy Tank, Get Out of Hell and Reshuffle cannot be sent to the Dead Deck. Brain Capacity and Quion Multipliers might be tricker but I am not sure of the inner workings of how those cards are "counted" inside the deck.)