My 7 year old 4 ton Carrier AC died.

My AC which is a 4 ton carrier started leaking for the 3rd time in a year, the coils went out, and it has been unable to maintain temapture. The wires got corrosion all over them. It is only 7 years old but it no longer works as it should. I decided to get a new AC as I already had the previous AC repaired once. They company charged my 9k for the new unit, redoing the AC closest wiring and filter system, increasing my AC slab size outside, and adding additional exterior installation. Not sure if thats a good deal.the are installing a American Standard AC. Let me know if it was a good deal and if AC just don't last as long these days.