My 90 yr old father was quoted $1100 for exhaust system. Does this seem correct.

What is wrong with the exhaust system? You need to find another shop to take it to.

I would recommend getting a second opinion from a trusted repair shop. We use both O.E. and aftermarket parts and give our customers the option. If the vehicle has only 53,000 miles, I can't see it needing it all replaced due to it being 409 stainless. Greg

I wonder are they quoting for a catalytic converter agree with the other answers get a second opinion.