In that case, who would ever pay the premium?

Vandroiy,
I am, again, going to make this quite simple for you. Paying a premium on shares and running them on deepbit is like gambling. If deepbit gets lucky, you get more coins than you paid. If deepbit is unlucky while you are running your purchase, you get less coins than you paid. Miners and pirate are the house in this case, winning every time a bet is placed. Purchasers are the gamblers trying to win big.
Best,
gigavps