The automatic response of the North Korean government would be introducing a prohibition. Or maybe that already happened, who knows.
This was occurring as recently as last year all over the world when commodity/food prices spiked. Anywhere you see black markets, you can find rationing and price fixing nearby.
I was in North Korea back in August, and bought one of each denomination as a souvenir. Guess they're going to be more valuable now.
Foreigners are not allowed to spend the North Korean won within the country. Instead, you pay in RMB, EUR, USD at locations approved to take foreign currency -- so we couldn't just go buy stuff at the same stores as the locals. Now I'm wondering how much of that foreign currency makes it back to the central government, given this news.