Wirelessly posted (BlackBerry: BlackBerry8530/5.0.0.601 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)

"Even on AA metal, TATL flights from LHR have taxes of about $170."

Not if the journey starts in DUS (or somewhere else outside the U.K.) and merely connects in London, rather than originating there. But you would still have to pay departure taxes associated with the origination airport, plus the LHR PSC, which applies even to connecting passengers.