My kid didn't understand until the vurtual items he bought with his hard earned money, about 80usd, vanished when the company shut down. It was a brilliant educational moment. Alas Minecraft is probably good for another decade!
Yeah your kid probably wouldn't have felt the 'blow' if he didn't work for that money.
The problem isn't virtual items, everyone pays money for non material experiences/services - and on a long enough timescale even material things wear down/break.
The important thing to teach a kid is if the value they derive from buy a skin eg. and whatever it brings to them (happiness, bragging rights) is more important that opportunity cost of paying for that.
If the cost is always zero (daddy pays) - then the kid will not stop to think about it ever.
Something about telling a kid that the iron is hot vs the kid needing to burn himself to learn.
