My other half owns a Renault Megane - the local Renault dealer wants £140 for a replacement/duplicate fob, which I would estimate costs less than £5 to manufacture.
Maybe such a cost will effect your future choice of vehicle manufacturer, when buying your next car.
Personally if I were you, I would get by with the one key - until the other turned up (which would probably happen as soon as you part with £140).