But printing the money is only useful in that it manipulates the market price to go that 10% higher which is where you make the profits.

If they printed that money and everyone found it worthless and the market didn't response they wouldn't have a business model.

Edit: I guess I should say that's the conjecture of those saying Tether was created purely for profit based on market manipulation. I don't have an inside knowledge on what was going through the heads of those at bitfinix who created it.