The switch is expensive because it contains a latching timer relay that operates the backglass defogger for ~10 minutes or so, then kicks off. This is important; you don't want to have a simple on/off switch, and the suckers draw a
lot of current so you really do want the relay (not just a simple switch) for safety's sake. No need to tempt fate by making a Ford even more fire-prone than it already is, eh! Probably easiest and fastest just to spend the $35 on
the last item on this page (new switch & timer relay with wiring).