Freon leak - fix or repair?

I was having a problem with my AC leaking water and had someone come look at it. They told me that the freon level was very low and recharged that (2 pounds). Apparently there is a leak somewhere. He said they charge $325 to find the leak and then 99% of the time it is one of 3 major parts that needs replaced and would cost between $1200 - $1500. He said we should decide if we want to proceed with that or just buy a new unit. Ours is 8 1/2 years old and I don't know what kind. He said it was a contractor's cheapie unit. Does this make sense?. Is it really usually that much to repair a leak? Thanks!