Observer wrote:
Got a quote today for a Trane 4 ton (replacing a 3.5 ton) XL15 outside
unit with a matching Trane coil inside. Installed was $7800. I'm
thinking a more fair price is $7000 but this is just based on some
brief internet reading.

Fair may be $6500 or $8500. None of us can see the job from here. We don't
know what pitfalls may be in this particular job, what obstructions, etc.
may be in place. Location and accessibility can add quite a bit to a job
also. Talk to a couple of contractors before you decide.