Shipping Damage Repair Costs

[Ace]

I recently sold a beautiful old euphonium that was in A+ condition. I carefully packed the instrument in its sturdy wooden case with lots of air bags inside. The outer shipping container was generously filled with packing materials. I thought the entire package was bullet proof, and I confidently left it in the hands of one of the two largest shippers. The buyer receives and opens the case, and discovers the bell has been bent back about 1/2" and is creased. Gawd, was this package dropped out of an airplane???

Question: Approximately how much will it cost to roll out the bell and make it look nice again? (BTW, the finish is satin silver.)