> 23k seems like a lot, especially so if the leak is somewhere other than a hidden part of the line.

I am inclined to agree. The rear 2½T unit in our rental blew a line last year. Two companies quoted my landlord $10k for a new 2½T condenser and air handler (1 was another renter of his). Even that seemed high to me but I could be out of date

In the end, I had a friend come out and look it over. Leak was near the compressor and he charged well under $1k for the fix, mostly for refrigerant.