I don't see why that would be the case. Enlighten me. If the market will pay yield X for a long-term bond of a certain duration, banks can make money by offeri

I don't see why that would be the case. Enlighten me. If the market will pay yield X for a long-term bond of a certain duration, banks can make money by offering mortgages for X plus some margin. The Fed selling MBSs should just depress yields in general.