Right, but if they acquire $6000 for 20000 tether (that they paid $0 for), and promise that tether is full redeemable for $20000, they are $14000 short when the tether holder comes knocking.

What if tether is the tether holder and they simply decide to never call in that debt against themselves? That would mean they lost their own money, but they still may have made enough money over the course of the entire scheme to pay off their "legitimate" customers and thus avoid getting publicly called out.

> What if tether is the tether holder

Why should they print more tether if they are already holding them?

So long as the printing press keeps running, the solution is to print yourself another 14000 in tether, convert to BTC and sell the BTC for 14000 in real USD.