LG gives credit to the phone's large 5.5 inch display, LTE connectivity, sensitivity and the UX. The Korean manufacturer decided to just pass along these results from the sales in its own backyard which averaged over 8000 units sold each day.
In the U.S., the LG Optimus G Pro is available from AT&T. The phone launched in the states on May 10th.
source: LG (translate) via AndroidCentral