leaking condenser

Purchase brand new 2015 GMC 1500 Sierra from Kirk Brothers in July 2015 and a year and half later, the air conditioning not cooling. There service wants to charge $1,012 to repair a leaking condenser. The explanation for this defect according to the service department was high mileage and other reason a rock probably hit the condenser. My guess is this truck was sold to us with this defect but if a slow leak, it took the problem now to manifest itself. I was highly upset and disappointed because a relatively brand new truck should not have air conditioner malfunctioning a year and half later. My 350Z Nissan is 14 years and the air conditioning is just as cool today as when I purchased it. Car dealerships charge an exceedingly high price for these vehicles but when it's time to honor the customers and merchandise, they always fail to deliver. I left without my truck being repaired but Kirk Brothers lost a customer today.