No idea on prices chop, but I was recently polybushing an evo 6 and 3 of the rear Aluminium suspension arms were split where the steel surrounding the rubber bush had choroded. quite hard to check, but if you can DO IT, they vary in price from something like £120 an arm to £280, this poor guy needed 3 Front brake discs warp fairly easily too.

These are very expensive cars to maintane and run, so bear it in mind.