That should make it even easier. If it has been securitized, the value of that security is way below par value. For example, your $500,000 mortgage at 2.5% might only be worth $300,000 on the open market. Somebody could buy that mortgage backed bond for $300,000 and offer you a $500,000 mortgage at 4% in exchange, resell that mortgage for $400,000 and pocket the $100,000 difference.

If I understand correctly, this is how the Danish mortgage system works.