https://www.google.com/flights/#sear...3;r=2017-10-02
BRU-FRA-PTY-IAH-LHR-BRU
Mid September until early October prices are below $420. It books in K class with a UA ticket number. Conversely, if you're a Miles & More member you can book directly with Lufthansa, but there is an increase on the price. Not significant, but not $405 dollars.
13,256 PQM about 3.1 cents per mile