MethodMissing.rb

class CarPart

  # does the method name end in _price ?
  def ghost_method_condition(name)
    !!name.to_s[/_price$/]
  end
  
  # rewrite method missing if the method matches ghost_method_condition
  def method_missing(name, *args, &block)
    super unless ghost_method_condition(name)
    # do something else...
  end

  # rewrite respond_to? to include ghost methods
  def respond_to?(name, include_private = false)
    ghost_method_condition(name) || super
  end

end
c = CarPart.new
puts c.respond_to? :stereo_price