Plus it doesn’t pass the smell test, there are plenty of photos online of danish mcdonalds menus going back to at least 2018, that I could find in two minutes of searching. That clearly shows a standard Big Mac meal is 60 Danish Krone. Which was 9 USD to 10 USD depending on when you pick the exchange rate in 2018.
In the US, depending on location, the same meal would have been 5.5 USD to 7 USD in 2018. Maybe a bit more in Hawaii.
Maybe there were a few places in Denmark selling it for much cheaper, and it was being compared to Hawaii prices, hence why this notion came about, but that’s a ridiculous stretch.