I suppose it depends on demand too, fn2's are relatively new compared to the ep3 so there may not be much demand. Look at brand new prices too knock off what you think is reasonable. It also depends on how much you want for them, if someone offered you £20 for the lot you'd probably say "f" right off!! So it is hard to say, People will buy it if it's a bargain. As a rough guide I would budget £40-£50 for airbox, £20-£30 for intake hose and £15-£25 for filter (imo).
Or you could keep them boxed away safe, (I've kept my airbox) you never know one day you may want to put the car back to standard.