15$ is to much for customs in Denmark, so the 15$ becomes something like 40$ for a promo, if caught during shipment.
How? That makes no sense.
15usd=~92dkk, which is above the minimum threshold of 80dkk if the shipment is "caught" you pay a fixed fee of 160dkk+25% VAT (92*1.25)+160dkk=~44usd.
Now if the price was 10usd + 5usd in shipping, the 10usd would be below the minimum threshold and you would not pay the fixed fee or the VAT. The 80dkk limit is without shipping but you do pay VAT of the shipping if above the limit.
Oh the joys of importing things from outside the EU.