I think it sound way high. Google "honda civic condenser replacement cost" seems to confirm. My car AC died last summer, and they just filled it with more gas, but added a tracer so they can tell where it's leaking. We haven't had it back since we barely drive it. Maybe shop around for prices. Are you sure they found the cause, and aren't just quoting the most expensive repair?
I once had a garage replace my alternator, and it turned out the real problem was an electrical short.