I presume they're arriving in Stansted on Ryanair/Easyjet/etc.. but if they're not, there are plenty of cheaper options available around EGSS.
Haven't checked out them out (runway length, opening hours etc..) but I can think of at least High Easter, Andrewsfield, Audley End (a short train ride from Stansted) & Cambridge (again, not too long on the train from Stansted) which are all presumably alot cheaper then Stansted.
FC