DO NOT pay the $780. You did some damage to the quad and you paid to fix it - that's all he can get. Sure, he can try to charge you for it but he'll never collect. Hopefully you did any payments via a credit card as you can cancel any disputed charges.

Bent rims are common. There is no way he can legally collect for his lack of parts in stock to keep his rental fleet up and running. This is a complete BS claim.

You paid for the rental. You paid for the damage. Walk away.

 

Thanks everyone for your great advice. I feel further justified in disputing and fighting the $600 of un-rentable time. I'm going to call other ATV rental companies and check if they normally stock a few rims. You would think that an intelligent business owner would carry items like this if renting every ATV in your fleet everyday is so important to your business. Thanks again.
P.S. My son and I had a blast before blowing out the tire!

 

I would also agree to tell him you want the old tire and rim. Otherwise, I would dispute the entire charge. If he is truly replacing it, that should not be a problem at all as you are paying for it.