“ If the veteran has contractual or legal recourse against a third party that would only, in part, extinguish the veteran's liability to the provider of the emergency treatment, and payment for the treatment may be made both under subsection (a) and by the third party, the amount payable for such treatment under such subsection shall be the amount by which the costs for the emergency treatment exceed the amount payable or paid by the third party, except that the amount payable may not exceed the maximum amount payable established under paragraph (1) (A) . ”