Sadly it doesn't work like that. It doesn't need any crypto mechanisms. Look at magic the gathering cards, it's pretty similar to Steem Monsters in the model I suppose. Cards lose value over time, because the company prints more cards that are good against X or Y. Or they reprint some high-value cards. Sure you still hold something, but the overall value of your collection declines through time.
Magic has a rule where certain cards on a list aren't going to be reprinted, for example, Black Lotus of Alpha & Beta. Those cards do hold their value and even rise with time. I'm pretty sure that's what SM is trying to achieve as well.