Yes. You are right on the first point. But not on the second.
Cards are priced in USD. So if you buy them now with steem. Your steem is locked and sold at the current price of 14 cents. Now essentially you own a different asset. Not steem anymore... correct?
Price of card can of course go down. Anything can go down. However, the concept it that you have a NFT now, and not steem. And like you said that NFT is priced in USD.
I think you agreed on that point already :)