Friend damaged a 214 rim on my X5

[evolver]

Today I let a friend of mine, a big BMW fan (3-series owner), drive my X5 for a little test-drive. I was with him in the vehicle. As we were leaving the garage, he made a 90-degree left turn and scratched left rear rim against the curb... The damage looks quite ugly. He is willing to pay for the repair. What is the best way to handle that? Polish it out somewhere? Have it replaced? Make a insurance claim? Can he make a claim on his policy to have the rim replaced?

I have 214 rims. Pristine after only 2 months of owning the vehicle.

How much a repair could be?

I'm upset, very upset...