How much does it cost to get scratches out of alloys? Or more accurately, how much am I likely to be charged.

I had a hire car last week and the place I got it from (Europcar) are claiming there's a scratch on both front alloys (made up bollocks by the sounds of it). The company who provided the hire car have written to me saying they've been informed of the scratches and I could potentially be billed for it.