I recently did some research on ducted Daikin systems in the Seattle area, and estimates were all in the $20K range, for full installation. The equipment itself may be ~$6K or so (not sure exactly), but it's the labor that costs a lot.
I’m just taking equipment cost here, this is in Australia (Air conditioning is extremely common here, and basically every unit is a reverse cycle heat pump too, so installation also seems very cheap compared to the US).
Just saying if the equipment cost of the whole system is well under $5K, it shouldn’t cost anything like that to replace a circuit board (which as others have said, the part probably costs $100 wholesale to the technician).
I recently did some research on ducted Daikin systems in the Seattle area, and estimates were all in the $20K range, for full installation. The equipment itself may be ~$6K or so (not sure exactly), but it's the labor that costs a lot.