The Steam Winter Sale started and lasts until Jan.2nd 2015.
X-Plane 10 is off 30%, now 38,49€ instead of 55€.
Seems to be the same in USD.
Check other Flight Simulations on Steam for price reductions as well!
(FSX is 4.99€ for the next 12-24 hours, Il-2 Battle of Stalingrad is now 38€ instead of 49€)