Originally Posted by
ISTFlyer
Add on, The price of the extra seat is the base fare + the fuel surcharge.
In other words, it's technically double the price of a single seat minus taxes & fees.
The old, unpromoted, way seemed much cheaper: maybe it was base fare only. i used it to get an empty seat between us when travelling with friend with a broken leg. Sadly the empty seat got shifted - some clever work was required at check-in to ge it sorted out.